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Making the Internet faster at Netflix

Making the Internet faster at Netflix

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Arbaz Nadeem
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June 26, 2020
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In our fourth episode of Breaking404, we caught up with Sergey Fedorov, Director of Engineering, Netflix to understand how one of the world’s biggest and most famous Over-The-Top (OTT) media service provider, Netflix, handles its content delivery and network acceleration to provide uninterrupted services to its users globally.

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Sachin: Hello everyone and welcome to the 04th episode of Breaking 404, a podcast by HackerEarth for all engineering enthusiasts and professionals to learn from top influencers in the tech world. This is your host Sachin and today I have with me Sergey Fedorov, The Director of Engineering at Netflix. As you all know, Netflix is a media services provider and a production company that most of us have been binge-watching content on for while now. Welcome, Sergey! We’re delighted to have you as a guest on our podcast today.

Sergey: Thanks for having me, Sachin!

Sachin: So to begin with, can you tell the audience a little bit about yourself, a quick introduction about what’s been your professional journey over the years?

Sergey: Yeah, sure. So originally I’m from Russia, from the city of Nizhny Novgorod, which is more of a province town, not very well known. And that’s where I got my education. I went to college from a very good, but also not very well known university and that’s where I had my first dream team back in 2009 when I was in third grade in college. I teamed up with my friends and some super-smart folks to compete in a competition by Microsoft, which is a kind of student contest where you go and create software products. In that year we were supposed to solve one of the big United Nations problems and what we did, we were building a system to monitor and contain the spread of pandemic diseases. Hopefully, that sounds familiar, but it’s what it was in 2009. And as a result, we had unexpected and very exciting success. We happen to take second place in the worldwide competition in the final in Egypt. And that was really exciting to be near the top amongst the 300,000 competing students. And it was really the first pivotal point in my career which really opened the world to me because the internship at Intel quickly followed and it was kind of the R & D scoped, focused on computer graphics and distributed computing. And a year after I was lucky to be one of the few students from Europe to fly, to Redmond, to be a summer intern at Microsoft. It followed with a full-time offer to relocate to the US upon graduation from college in 2011. At Microsoft, I worked in the Bing team helping to scale and optimize the developer ecosystem, particularly the massive continuous deployment and build system for the Bing product that Microsoft. That was a really exciting journey, but the relatively short one, because quickly after an unexpected, the referral happened to me with an invitation to interview for the content delivery team at Netflix, that was just kind of getting started and to help them build the platform and to link and services for the content delivery infrastructure. And quite frankly, I don’t expect that I’ll make it, but I couldn’t pass the opportunity at least to interview. But somehow I made it, very early in my career. I was 23 years old with just a few years of practical experience and it was quite stressful to join the company. I was on an H1B visa. I lacked confidence. I lacked a lot of, kind of relevant to and can experience in that area. Yet I gave it a shot, and I joined a team of world-renowned experts in internet delivery. And, um, I stayed there ever since. I will say that that decision and that risk that I took was the second big milestone in my career. Because from there it allowed me to grow extremely quickly and it allowed me to be truly on the frontier of technology and shape my mindset working for one of the top kinds of leading companies in the Silicon Valley, I’ve been here for about eight years. I initialized, I stayed on the platform and tooling side. I built a monitoring system, a number of data analysis tools. The overall mission of the team is to build the content delivery infrastructure, to support the streaming for Netflix. And over time, we added some extra services on top of pure video delivery. And a few years ago, that’s the group that I joined still staying within the same org, working on some of their extra advanced CDN like functionality, specifically developing some of the ways to accelerate the network interactions between clients and the server, uh, helping to better balance the network traffic, the traffic between clients and the multiple regions in the cloud. And I also worked a little bit on the public-facing tool. So I built the speed task called fast.com, which is one of the most popular internet testing services today powered by open connect CDN. And as of today, I’m a hands-on engineering leader. I don’t really manage the team. Instead, I work extremely cross-functionally with partners and folks across the Netflix engineering group. And I help to kind of drive major engineering initiatives in areas related to client-server network interactions. And I have to improve and evolve different bits and pieces of Netflix infrastructure stack.

Sachin: Thanks so much for that and it’s an amazing journey. You know, it’s really inspiring to see. Um, would it be fair to say that, you know, you kind of didn’t, it’s been serendipitous for you in some sense, did you plan to be here in the US and you know, be working in an organization like this or it all just happened back when in school, when you decided to participate in the Imagine cup challenge?

Sergey: Well, I wouldn’t say that I didn’t want to do that, but I definitely didn’t expect to, and I definitely didn’t expect to be in a place where I am today. I would say that my whole career was a very unexpected sequence of very fortunate events. I guess, in any case, I was sort of seeking those opportunities and I was not afraid to take a risk and jump on them.

Sachin: Yeah, that’s super inspiring for our audience and, like you correctly said, you got to seek those opportunities, and of course you need a little bit of luck, but if you’re willing to take those risks, doors do open. So, definitely very inspiring. Uh, so a fun question for you. What was the first programming language you, you ever recorded in and you still use that?

Sergey: Yeah, that’s a really interesting question. Um, the first language that I used was Pascal. And, uh, it was when I was 14 years old. So I started my journey with computers relatively late. And so it was kind of in the high school at this point. And the first lines of code that I wrote were actually on paper and I was attending The Sunday boot camp, led by one of the tutors who was preparing some of the folks to compete with ACM style competitions, where you compete on different algorithmic challenges. And he did it for free just for folks to come in. And someone mentioned that to me. I was like, Ooh, that’s interesting. Let me see what it’s about. And for the first few months, I was just doing things like discussing different bits and pieces about programming and all I had was a paper to write different things on. Later on, I of course had a computer and the first few years of Pascal was the primary entry for me to programming. And it was primarily around CLI and some of the algorithmic challenges. It’s only a couple of years ago when I discovered the ID and the graphic interfaces, and it really opened the world of what they could do. Uh, so yeah for me the first programming language is Pascal. And no, I don’t use it, but still have very warm memories of that because I think it’s a really, really good language to start with.

Sachin: Writing your first piece of code on paper. That’s an amazing thing. The folks who are getting into computer science today, they get all these IDEs, autocomplete, you know, all the infrastructure right upfront. Uh, but I think there is some merit in doing things the hard way. It prepares you for challenges and that’s my personal opinion.

Sergey: Yeah, I definitely agree with that. I’m not sure whether the fact that they had to go through that is an advantage or disadvantage for me, because I really had to understand the very basics and fundamentals. And I was super lucky with a tutor for that. He really didn’t go to the advanced concepts until I really nailed down the fundamentals. And I think having to really painfully go through that, if you’re kind of using a pen and sheets of paper, I think it really forces you to really get it.

Sachin: Right. Makes sense. So Netflix is one of the companies that has been growing massively over the last few years and acquiring millions of users. What are some of those key design and architecture philosophies that engineers at Netflix follow to handle such a scale in terms of network acceleration, as well as content delivery?

Sergey: Yeah, that’s an excellent question. In my case, as I mentioned, I’ve been here for quite a while and I had a lot of fun and enjoyed watching Netflix grow and be part of the amazing engineering teams behind it. But quite frankly, it’s really hard for me to summarize the base concept like use cases, there are so many different aspects of Netflix engineering and challenges, and that there are so many different, amazing things that have happened. So I’ll probably focus a little bit more on some of the bits and pieces that I had on the opportunity to touch. And for me, the big part of the success of growth was actually a step above the pure engineering architecture. It’s firstly rooted in the engineering culture because the first Netflix employees are great people. But second and most importantly, it really enables them to do the best work and gives them a lot of opportunities and freedom to do so. And with that empowerment and freedom to implement the best and to do the best work, I think the engineers are truly opening themselves up for the best possible solutions that really advance the whole architecture and the whole kind of service domain. On the technical side, in my experience, what I think was fundamental to effectively scale infrastructure is the balance that we have had between innovation and risk. And in our case, many fundamental components of our engineering infrastructure are designed to be extremely resilient to different failures and to reduce the blast radius, to contain the scope of different issues and errors. With that’s really embedded like this thinking about errors, thinking about failures, it’s really embedded in the mindset and that leads some of the solutions and some of the implementations to be really robust and really resilient to some of the huge challenges and lots of unexpected demands. And in that aspect is that many systems I designed and thought of to scale 10 X from the current state. So that’s often when we think about the design, we don’t think about today. We think about the 10 X scalability challenge, and that includes both architecture discussions and some of the practical things like performing the skill exercises constantly and stress testing our system, both existing and proposed solutions and constantly making sure that things can scale. So in case, we have unexpected growth, we have confidence that we can manage it. And I think as a result of that, we are not only getting an architecture, that’s stable and scalable. But we also get an architecture that’s safe to innovate on, because we can do the changes with more confidence that we can roll back things. We have confidence in our testing and tooling and with that confidence, I think it’s much as much easier to apply and do your best.

Sachin: Interesting. So you spoke about designing for innovation as well as being resilient and then kind of designing for a 10X scale in the very beginning. So typically, and this is my experience and I may be wrong here, but when we were younger in our journey as a software engineer, right, we tend to get biased towards building out the solution very quickly and, do not have that discipline to kind of think about the long term scale and all of those challenges, because that is very deliberately put that in place. Right. So, so has there, like, how did your journey kind of evolve in that? Are there any tools, techniques that you use to kind of force yourself to come up with the right architecture? Could you talk a little bit about that?

Sergey: Well, so I think you were what you touched upon a really great point, but it’s, I would say it’s a slightly different dimension, a bit more of a trade-off between the pace of innovation and sort of the technical debt, the quality of code, so to speak. And I think this is an extremely broad topic, uh, with where I would say their answer would really depend on their application domain. For example, I would give you one answer if you were working on some medical or military services, versus some ways like a social network, consumer and product entertainment sort of services because the risk of failure and the mistake is completely different in that case. And I think another factor comes from the understanding of the problem. There is, I think, a big difference in designing the system for the problem that you understand really well, and you have a pretty good idea that it’s there to stay for quite a while versus more of an exploration where you’re not exactly sure whether this would work or not. You are still trying to kind of get a hand at it. And, uh, quite often you start with a second, with a latter option, and that’s what made you start to do. And I would say that in that case, uh, in my personal experience, I think it’s much more productive to focus on the piece of innovation. And, uh, maybe in some cases build some of the technical debts, maybe in some cases to compromise some of the aspects of the best practices but being able to get things out and get some kind of bits and pieces really quickly and learn from it. And since you are relatively lightweight, it’s much easier to pivot and change direction. At the same time, it doesn’t mean that we all have to be Cowboys and break things here and there. There is a balanced approach. You can still invest in the core principles and the core architecture that allows all those things innovations to happen safely. And I think at Netflix, that’s what really we excelled at. We have some of the core components, some of the core tools that are available for most of the engineers. That’s allowed to make things, uh, and innovate safely while not being overly burdened by some of the hard rules and, uh, some of the complicated principles and gain that experience. And I would say this is sort of a natural process. You have something that’s done relatively quickly. Then you were at this kind of crossroads. Whether now you know, this is a real thing and you’ll have to scale it. And then you would likely apply a different way of thinking or maybe it doesn’t work and well you save a bunch of work by not overcommitting to something really big before confirming that this is useful. And at this point when you were on the road to actually build it for the long term, it might be the proper solution to rebuild what you’ve designed in the past. And it might sound like you were wasting a lot of time. Like you’re doing the double effort. But the way I see it, there’s actually, you’ve saved a lot of time because you were able to relatively cheaply test a bunch of lightweight solutions. You got the confidence, what really works. And now you’re only investing a lot of resources on building the long term for the one thing, and essentially you’ve saved all the time by not doing that for all other ideas that you’ve had. Um, I have them all, it’s sort of a 20, 80 rule that takes 20% of the time to build a working prototype and it takes 80% of the time to productize that and make it resilient and scalable. Um, in many aspects of innovation, it makes sense to start with the 20 and only go for the 80% over time. Yeah, but as I mentioned, it doesn’t mean that everything has to be all or nothing. There are still major principles and it definitely makes sense, especially as you get larger to invest in the main building blocks to enable those things to happen safely. There are always some of the quantum principles that are cheaper and easier to follow in all scenarios. I think one of my favorite books that I was lucky to read early on is the Code Complete by Steve McConnell, which goes into the lots of fundamentals about just writing good and maintainable code, which in most cases doesn’t take more time to write. I just need to follow some relatively simple guidelines.

Sachin: Gotcha. That’s a very interesting perspective. If I were to summarize it, you were saying that, uh, architecture design is context-dependent. You got to know what the problem is and what you’re optimizing for. And sometimes you’ll go for something lightweight and then optimize it later on because the speed of innovation is also important, but there are always certain principles that one can use without really increasing the development time, certain strong arteries that can help in building robust code. So that’s, you know, definitely interesting. Uh, another fun question. Do you get time to watch any shows, movies on Netflix, and if so, which one’s your personal favorite?

Sergey: Yeah. Well, while often I don’t have a ton of time to watch I definitely love to have an opportunity to relax and enjoy a good show and Netflix is naturally my go-to place for doing that. And, I’m in a losing battle to keep up with all the great shows that I would like to watch. And, um, it’s quite hard for me to choose one favorite. So I think I’ll cheat and I’ll choose a few instead of just one. So I hope you’re fine with that. I think one thing is I’m a fan of sci-fi as a genre and I really enjoyed Altered Carbon, especially the first season. And over-time I’m also learning that I’m affectionately a fan of bigger shows that I have no idea about. And the one title that I really enjoyed was ‘The End of the F***in world’, which is a dark comedy-drama. It follows the adventures of two teenagers. It’s a really kind of unique piece of content and I truly enjoyed every episode of it. I’m really glad that as a company, we really invest in more and more international content, not just coming from the American or the British world. And the latest favorite for me was ‘The Unorthodox’, which is a German American show with most of the dialogues actually in Yiddish, which is a part of the Orthodox Jewish culture. I enjoyed both the personal story and I also learned a lot about it because I had no idea about this part of the cultural experience for some of the folks. I was both enjoying the ways, done the story behind it, and it had a huge educational component.

Sachin: Thanks for sharing that. So moving back to the technical discussion. So you worked at multiple organizations, you know, Intel, Microsoft, while having the bulk of your time you have spent at Netflix. If you were to look back and think about one or two major technical challenges that you faced and is there something that you would like to talk about and more so along the line of how did you overcome it?

Sergey: Sure. So I think I’ll probably choose one of my favorites. And I think that’s the biggest challenge that I can recall probably by far. And that was my first major project when I joined Netflix. So the task was to build the monitoring seal system for the new CDN infrastructure. And, that was really quick as the task quickly forwards after I joined the CDN group at Netflix. As I mentioned, I was relatively early in my career. I was relatively inexperienced. I know very little about this domain and there’s a huge infrastructure that’s about to like, is being built and we are migrating a lot of video traffic on it. And this is a huge amount of traffic. At that point, Netflix was about one-third of all downstream traffic in North America. So like a third of the internet is there. And here I am like a new employee, that’s not like, Hey, let’s go see some that will tell us how we do like that. We’ll monitor the main state of the system. Like you will, you’ll have to design the main metrics. And really design the system end-to-end on both the backend and the front end, that of UI. And in the true Netflix culture was given the full authority to make its own tactical decisions on product design and implementation. So it was just a full-on like, here’s the problem context, please go and figure it out and we are sure you’re, you’re going to agree. And The biggest challenge of all of that is that many aspects of the system were new and quite unique. And even the folks who were working on this history for a long time, they were quite upfront that we are learning as we go in many ways. So we cannot really give you the precise technical requirements, but we actually wanted to look at. And overall we wanted to keep the whole system and the approach to the monitoring as hands-off as possible, just to make sure that the system reflects some of the architectural components, which reflect some of those principles like a self-healing system that’s resilient to individual failures. So I had to fully understand the engineering solution. I had to model it and there, in terms of the services and the kind of data layer. I had to look at and partner really closely with the operations team to learn a lot about how the system performs, what metrics we should look at, what’s noisy, what’s not. And it’s been quite a ride but especially remembering that was an extremely fun challenge. And I think some of the things that were fun like: a) That I was very unexpected, given the huge responsibility on a pretty critical piece of Netflix infrastructure stack and I was given full control of what I’m using for that. And I could either choose something that I’m comfortable with or something that’s completely new to me. There were really fun interactions with various folks, even though some of my teammates were not necessarily experts in building cloud services or building UIs. There were many other folks at the company who were extremely open and helpful to get me up to speed. I think some of the things that have allowed me to where success is that system is still used today with lots of components still the same as they were built many years ago. I think I made the right decision to focus on very quick iteration. As a matter of fact, the first version of the system fully ready for production and actually used by the on-call by the operations team was done in about two months. And that with me learning how to deploy ADA services in the cloud. I chose Python as a framework, and I knew very little about it before I learned the new UI framework and kind of built the front end in the browser for it. But focusing on the initial core critical components and getting something working was a huge help because it allowed me to build a full feedback loop with the users and started to start learning about the system. And then that calibration of the stakeholders allowed it to iteratively evolve it over time. And even though I didn’t know a lot of different things early on, I was extremely flexible and adaptable. I think some of the key things that were critical for my success to get it done is my ability to wear my mistakes, to be very upfront about mistakes, and actively seek help. And I think that’s one thing that I often notice, different people are not doing for various reasons. They think that it’s not the key to make mistakes, or they are somewhat unskilled or unqualified if they ask for help. For me, it’s been always the opposite. No one, nobody knows everything. Nobody’s perfect. Everyone, everyone makes mistakes. And, uh, the sooner you realize it and the more upfront and open you are around those aspects. The better you’ll be able to find the ideal solution and the faster you’ll be able to learn over time.

Sachin: Right. So it would have been a lot of confidence for you back in that time. Like you said, you were early in your career and the organization just said, Hey, this is your project. You have complete authority to just go out and do. And when we know, we’re sure you do the right thing, it must have also given you a lot of confidence, right?

Sergey: Well, quite honestly, initially it didn’t. Initially, it freaked me out because I was especially after companies like Intel or Microsoft, where their approach is very different. And I only had a few years of experience and I was not a well-known expert. That was very unusual. It was very scary. I would say the confidence really came months later when I was starting to see that the key is something that’s been built, that’s been used, I’m getting good feedback. And people are thanking me for working on that. They are giving some constructive feedback. They make suggestions, and I’m becoming the person who actually knows how to do it. Then in some of the domains, I’m becoming the most knowledgeable person, which is natural when you’ve worked on that. I would say confidence really came at this point, which was many months after that I would say probably a year or so. Maybe even after that.

Sachin: Got it. That makes sense. So, moving on to the next question, do you believe engineers should be specialists or generalists and how does this really impact career growth in the mid to long term?

Sergey: Yeah, that’s a great question. And personally, I don’t think there is one right style. To me, it’s like comparing what is more important, front end or backend. I think any effective team requires both types of personalities. And for nearly any major project, you need to rely on those because if you think about it, if you have a team of only specialists, you’ll have really well done individual pieces of the system, but it will be really hard to connect them together. Similarly, if you only have generalists, you may have liked a lot of breaths, but it would be really hard to actually build truly innovative aspects of the products because that’s the point of focusing on the one area that you have to give a compromise and not know something else. I think ultimately for effective teams, you need both times and you really need to have effective and efficient communication between both groups of them. You need them to be able to work together as a very well-aligned team. Uh, so yeah, I think for me personally, like what type of engineer to be is more of a personal choice. And also in my experience, there have been many opportunities to change the preference. You don’t have to necessarily pick ones and stick to that. You can mix it as you can go into one area or another. In my case I’ve been a specialist at some point and actually in the early stages of my career, I was probably the most specialized. When I was at Intel, it was a heavily dedicated area focused on computer graphics. I was optimizing some of the retracing algorithms and methodologies, what specific types of the network of Intel hardware. So it was all of low-level C, assembly, and some of the specific Intel instructions for, to get the most out of it. At Microsoft, I worked on search and some of the developer experience, then I switched to network and networking. So it’s, it’s sort of a mix. So I think I was becoming more of a generalist over time. On the tactical stuff, but still, I’m specializing in which area on the larger area. But this is also a personal choice and the industry and the technology is moving so fast that even if you were the expert in one area, very specialized today, in fact, years, you might, if you’re not keeping up, you might be off-site or that area is not everything. And you don’t have to stay there. You may find the passion somewhere else and switch to it. Or you can always stay as a generalist and just explore and move alongside technology growth.

Sachin: Yeah. So if I, if I were to summarize that, uh, you’re saying teams eventually need both kinds of engineers, and it really boils down to a personal choice, whether you want to be a specialist or a generalist, but, you know, given the current pace at which like you said, technology is evolving, it’s really hard to just be narrow jacketed into one thing, you know, because things around you would just constantly change and then you’ll have to adapt to them.

Sergey: Well, I think it’s on the latter point, I would say, I would say really depends. There are some of the areas that remain relevant, uh, for quite a while, for example, talking about the networking area, we’re still using TCP and that’s the technology from the 1980s. And there is still a lot of really interesting research and developments going on. And if anything, in recent times, the pace of development has accelerated. And yet, someone who specialized in that in the nineties would be still very relevant today. So in some of the areas you can still, you can specialize and you’ll be growing your influence. You’re growing your impact over time, but there’s no guarantee and it’s really hard to predict those areas. So I think, well, if you’re really passionate about it, it makes sense to stay. But I would say you should always be ready to pivot go and dig into something else.

Sachin: That makes sense. So another fun question, which software framework or tool do you admire the most?

Sergey: I think my answer will be probably quite boring at that. I’m pragmatic, I don’t have a favorite intentionally. I tend to follow the principle that there is always the right tool for the job. And as that principal and trying to avoid any sort of absolute beliefs or absolute favorites. Having said that, uh, the very few frameworks that I personally like and they’ve helped me quite a bit. I like Python quite a bit for its simplicity, its flexibility. From personal experience, it’s one language I was able to deliver a fully usable work in projects that are being consistently used for several years after in just two weeks. And before those two weeks, I barely knew Python. So I think that shows the extreme power of the language, how easy it is to pick up and do something actually practically useful. Related to Python, I like pandas quite a bit, which is a statistical library with some of the ways to do time serious or data frame analysis. From the network world, I should mention Wireshark, which is a general tool and it’s fantastic and definitely go-to for me to understand all that happens on the network communications at an insane level of detail. In terms of overall impact, I should mention the Hive, which is a big data framework. While it’s becoming sort of obsolete technology right now replaced by Spark and all of the following innovations. I think it’s really created a revolution in many ways. In its own time, creating, making it possible to access enormous amounts of data, very easily using the very familiar SQL like language. And for me, I happen to use it around the time and it really had a massive impact on a number of insights into things I was able to do.

Sachin: Interesting. I agree with you on the Python bit. I myself learned Python very quickly and saw the power of the framework and the versatility in terms of the things that allow you to do, like there’s hardly any industry domain, where, where you can’t use Python to very quickly prototype. Right? So in that sense, it’s a very powerful and versatile framework. Thanks for that. Let’s move on to the next one. You know, given the current scenario around COVID-19 everybody working from home, what’s your take on remote engineering teams? Personally, what do you feel about remote work and you mentioned that your work involves a lot of cross-team collaboration? So how has that been impacted positively or negatively in recent months?

Sergey: Yeah, so I think for the first question for remote work in general, the group that I’m in the content delivery group at Netflix, we were remote from the ground up. So our teammates, they are all scattered around the globe all the way from Latin America, to the US, to Europe, to Asia and all the way to Australia. In terms of working remotely we’ve figured out the way to do it very efficiently, but what’s challenging is that now we are a hundred percent remote because what you’ve done in the past, like some of the folks that are in the office, like in Los Gatos in California, some of the folks that are working from home and we effectively collaborate with each other, but every quarter we will do what we call the group of sites where everyone would get together in the same place. We will have a number of meetings and discussions, both formal and informal, where you’ll be able to sort of put the actual person to their image that you see on the screen. And you’ll be able to really know those persons, those folks, your teammates outside of their direct work domain. In my experience, that’s hugely impactful in terms of affecting your future interactions and building a relationship and working together as efficiently as possible. And with today’s COVID-19 world, we are losing that. So we are 100% remote and even though it hasn’t been a hugely long period of time, based on some estimates, it might take a while for us to work the way. And, it’s a challenge not to have some of that context and to lose some of this nonverbal thesis of communication. To your question, it’s also much harder to build new relationships. I would say it’s still possible to sustain some of the relationships that you’ve built from the past based on previous work together, previous interactions. But when you have to meet a new partner or when there is a new person joining the team, it’s extremely hard to find the common commonalities or find the same language, when you only have a chance to interact via chat or VC. I would say we are definitely trying different things to fix that. We haven’t found the perfect solution. We hope to find it. I would say we also call that you won’t have to find it for the longterm. Hopefully, the COVID-19 situation will be addressed as quickly as possible. But yeah, that’s the very few things that I would say that’s becoming even more critical. First is extremely clear and efficient communication. It becomes paramount and the sharing of the context, and especially from the leadership side, it becomes extremely important to make sure that everyone is on the same page. And that you really need to double down on all of the context sharing in that sense. And, uh, in terms of the partners, I think it’s extremely important to make sure that folks feel safe when they work that way. Because as part of not having a chance to talk face to face, it’s a great environment too, uh, for some sort of or kind of fear and paranoia to build up. Um, it’s harder to make sure like how you’re doing, how things are going, especially when there’s lots of stress happening on the personal side as well and there is lots of research that shows that we are not productive when we are experiencing high levels of stress. And, uh, I would say that’s on the individual side. It’s really critical to make sure that both yourself and all the partners around you are feeling safe and in the right state of mind primarily. And then it comes down to where something that’s really difficult, which is building trust between each other to do the best work. Even in the case, when you are very far away from each other, you really need to make sure that once you share it’s all the context about the problems, about the solutions, about the ideas. You have the full trust in others to do the best work to address some of the things and help you with some of the things or ask you for help as well.

Sachin: Got it. That makes sense. I completely agree with you on the fact that. Having a shared conversation in person is definitely different from having it over video and the kind of relationships that get built subconsciously is very, very hard to replicate that on video and, and I’m with you that hopefully, we can safely return back to work at some point in time sooner, rather than later.

Sergey: In the meantime, but one sort of thing that we are doing is that we are making sure that we still communicate informally. One thing that we do as a team, we have three times a week, we have a virtual breakfast. If someone can’t make it that’s okay. But otherwise, folks just have an informal breakfast together. And we tried to talk about things unrelated to work, uh, just any subject, basically something that you would have as a conversation if you went for the team lunch outside.

Sachin: That’s interesting. And is that working out well, like, do you see people interacting and joining these discussions?

Sergey: In my opinion, yes. I think personally I feel much more connected after those things. When I have an opportunity to hear and see folks discussing aspects outside of the specific tactical work domain. I think it’s useful for others. It’s good for morality. And I’m seeing that many other teams experimenting with different ideas along the same lines.

Sachin: Nice. So, onto the next question, you know the tech interview process is talked about a lot. People have their different opinions. What’s your take on given the current norms around tech assessments and interviews? What do you think is unoptimized today or what in your opinion should be changed?

Sergey: Cool. Would you mind clarifying, are you asking specifically about the current, highly remote situation or interviewing in general?

Sachin: Tech interviewing in general, the process that, you know, that is there. I’m assuming Netflix, other than the cultural aspects, maybe from a talking perspective and your previous organizations have had similar methods or processes. So do you think there’s something that we could do better? Not in the context of COVID-19 per se, but in general.

Sergey: All right, got it. I think it’s generally, I think there are lots of challenges with a typical interview process. And if you think about it, the typical interview experience where we have someone coming in for 30-40 minutes, solving some of the specific problems on the whiteboard, or sometimes on the shared screen, it’s not exactly what we experience in the day to day life. Quite often the problems are not very well defined, but you very rarely have specific constraints on time to solve it. Most of the time or I hope almost all of the time, there is much less stress in the typical work environment and you’re relating the person to something that they might not have the subtle experience in the workplace. At Netflix, many teams do try different – different approaches. We don’t have a single right way that everyone has to follow. Depending on the team, depending on the application domain, often depending on the candidate, folks will try to adjust the interview process. In our case, what we have tried and what we genuinely try to do, we’re avoiding very typical whiteboard questions. We try to focus on some of the problems that are much closer to real life. We try to lean on some of the homework, take-home assessments if possible. If the candidate has time to perform that and a general, I think this gives a much better read of the candidate skills because they can take it in the environment that they’re used to. There is no stress. There is not someone looking over the shoulder. And you can assess a much broader range of skills, not just a specific, like, I know how to solve it the way I don’t know how to solve it, but how do you write code? How do you document that? How do you structure it? And in some cases like even how do you deploy it? And those operational aspects of coding is a big part of engineering life, which are extremely important to assess as well. And I would say generally it’s a huge benefit if a candidate has something to share in the open-source and the open environment. If they have a project that someone can just follow or can take a look at the code, I would say that’s one of the best assessments of the skills it has just working, that’s been used, and that has been produced. It still doesn’t cover all aspects of it. It’s really hard to assess the qualities like teamwork or some of the compatibilities with the teammates. Um, those areas tend to be quite freaky. Um, and honestly, I don’t think I have any ideal solutions for that other than to make sure that as many partners for the new hire as possible are actively participating in the interview process. They have the ability to chat a little bit more and get an idea of whether they can work with a specific person and achieve strategies to do that depending on the team size or particular situation.

Sachin: Got it. So if I were to summarize this, if the interviewing process can be as much as possible, close to the actual work that you’ll be doing, while eliminating or reducing the stress that one goes through in the interview process, that should bring out a more fair assessment of the candidate.

Sergey: I would say, yeah, at least that’s the general strategy that in my experience, in the interview processes, I tend to follow.

Sachin: Interesting. So, another fun question, if not engineering, what alternate profession you would have seen yourself excel in?

Sergey: I would say it really depends on the time when you would ask me. I happen to get excited very easily and my immediate passions change quite frequently. As of recently, I would say I could easily find myself having a microbrewery or running like a barbecue-style restaurant. So those are the two things that I found interesting and I’m doing quite consistently for the last few years. I homebrew in my garage. I also have a few kegs of homebrew on top. And I have three grills in my backyard and those things complement each other very nicely and they bring lots of joy to myself and my friends as well.

Sachin: That’s really nice to know that you have a home brewery and you said you’ve been doing it for two years now.

Sergey: Uh, well, I would say more about five years.

Sachin: That’s an interesting hobby. Uh, so, you know, with that we are almost towards the end of our podcast. The final question today: So if there was like one tip that you could give to your peers, people who are at a similar role and even to those people who want to step up and, you know, come to a role where you are today, what would that be?

Sergey: I think I would respond with sort of a catchy phrase from our Netflix culture deck. And I think that defines the leadership style that the company tends to follow and that I personally strive for, which is leading with context and not control. And what that means is that as a leader, learning to gather, summarize, and effectively communicate the most critical goals and challenges that the business, you, your group faces and effectively share it with the team but trust the individual contributors and your partners to find the most optimal solution and execute it and not trying to do both at the same time, which is really hard to do it, but that’s, that’s what often happens. Because I think that empowering the folks with the proper knowledge and the kind of context around the problem, encourages folks to fully own it and better understand it and they become much more committed to that. And that has a much higher chance to provide the best optimal solution versus the situation when someone just tells you what to do like ABC. And that you’ll get more commitments. I think it inspires folks to grow much more. And I think overall it makes the person who is able to foster such an environment a much better leader, which is also extremely challenging to do. You’ve asked me for advice like for the managers, directors. I’m not sure I’m qualified to give that advice. Uh, it’s more of some things that I’m working on to prove myself and, as someone who is relatively new to their engineering leadership role, I’m finding lots of challenges and struggles, and also those things where you feel like, uh, you might know various aspects of the solution, but you don’t really have to be actively involved in every bits and piece of it and balancing those things is a huge challenge. And personally, as I progress on those, I see that I’m becoming more efficient and more useful for the group and for the company. And I think it’s a kind of ideal and useful goal to live by.

Sachin: So it’s more about empowering people so that they can find their own solutions. And then certain times you may even have the right solution in your hand, but you don’t want to do it because you want the people to fight their own battles. And maybe they come up with something completely different that you might not have imagined. So fostering that innovation is important.

Sergey: Yeah. I would say empowering with the context around the solution and empowering down with the trust for them to execute on it and fully own the implementation.

Sachin: Makes so much sense. And I think you’ve gone through the same in your journey at Netflix. From the early days, you got the context and you got full control.

Sergey: Absolutely. Yes, I experienced that and the full power of it as an individual contributor. And now I’m actively trying to get better at doing that for others as well.

Sachin: Yep. That makes sense. Sergey, it was a pleasure having you today as part of this episode, I really appreciate you taking your time. It was informative and insightful, and I definitely enjoyed listening. I hope our listeners also have a great time listening to you.

Sergey: Thanks a lot, Sachin! session. It’s been a pleasure to have a chance to share my story.

Sachin: Thank you. So, this brings us to the end of today’s episode of Breaking 404. Stay tuned for more such awesome enlightening episodes. Don’t forget to subscribe to our channel ‘Breaking 404 by HackerEarth’ on Itunes, Spotify, Google Podcasts, SoundCloud and TuneIn. This is Sachin, your host signing off until next time. Thank you so much, everyone!

About Sergey Fedorov
Sergey Fedorov is a hands-on engineering leader at Netflix. After working on computer graphics at Intel, and developer tools at Microsoft, he was an early engineer in the Open Connect — team that runs Netflix’s content delivery infrastructure delivering 13% of the world Internet traffic. Sergey spent years building monitoring and data analysis systems for video streaming and now focuses on improving interactive client-server communications to achieve better performance, reliability, and control over Netflix network traffic. He is also the author and maintainer of FAST.com — one of the most popular Internet speed tests. Sergey is a strong advocate of an observable approach to engineering and making data-driven decisions to improve and evolve end-to-end system architectures.

Sergey holds a BS and MS degrees from the Nizhny Novgorod State University in Russia.

Finding actionable signals in loosely controlled environments is what keeps Sergey awake, much better than caffeine. This might also explain why outside of work he can be seen playing ice hockey, brewing beer, or exploring exotic travel destinations (which are lately much closer to his home in Los Gatos, California, but nevertheless just as adventurous).

Links:
Twitter:@sfedov
Website:sfedov.com

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AI Interview Tools: Keep Humans Where They Matter

How to use AI interview tools without losing human judgment

Automate the parts of screening that humans do badly anyway — consistency, scheduling, identity verification, and rubric application — and protect the parts humans still do better: context, judgment, and read-the-room calls. That is the practical division behind every AI hiring rollout worth running.

If you're a recruiter or hiring manager evaluating AI interview tools — software that conducts, scores, or supports structured candidate interviews using machine learning — the question is rarely whether to adopt them. It's where to draw the line. The mistake we see most often is binary thinking. Teams either bolt an AI interviewer onto the top of their funnel and call it done, or they refuse to use AI-assisted screening at all because "hiring is human." Both positions miss the point.

This guide explains where AI interview tools create value, where human involvement remains essential, and how hiring teams can implement automated interviewing without sacrificing hiring quality.

What are AI interview tools?

AI interview tools are platforms that automate specific parts of the hiring process. Depending on the use case, they can:

  • Conduct structured interviews
  • Ask standardized questions
  • Score responses against predefined rubrics
  • Verify candidate identity
  • Detect suspicious assessment behavior
  • Schedule interviews automatically

Note: some vendors in the broader market also offer note-taking, transcription, and post-interview summary features under the label "AI interview assistants." These are general market capabilities and are not part of every platform, including HackerEarth's. Buyers should verify which features any specific product supports.

What these tools share is the ability to introduce consistency into hiring processes that are often highly variable.

Types of AI interview tools and where each fits

Organizations typically use AI interview tools in several ways. AI screening interviews are used for early-stage candidate evaluation and high-volume hiring — for example, screening 500+ applicants for entry-level software engineering or customer support roles before committing recruiter time. AI technical interviews evaluate technical skills using structured coding exercises and predefined scoring criteria, common for mid-level engineering hiring at companies like Atlassian, Stripe, or similar volume technical employers. AI proctoring tools focus on fraud prevention and identity verification during remote assessments — increasingly important as remote-first hiring becomes standard. AI candidate evaluation platforms help recruiters compare, rank, and shortlist candidates based on structured frameworks, typically integrated into an ATS like Greenhouse or Workday.

Most hiring teams use a combination of these rather than relying on a single solution. HackerEarth's technical assessments and OnScreen interview platform cover screening, technical evaluation, and proctoring in one workflow.

Why AI hiring tools matter for recruiters today

The biggest challenge in hiring is not attracting applicants. It is generating reliable hiring signals.

Human interviewers are naturally inconsistent. Different interviewers ask different questions, evaluate candidates differently, and often rely on intuition rather than structured evidence. For a recruiter managing 40+ open requisitions, that variability means two equally qualified candidates can receive opposite recommendations depending on who interviewed them.

A working paper from the National Bureau of Economic Research by Bo Cowgill (Columbia Business School, 2018), "Bias and Productivity in Humans and Algorithms," analyzed over 300,000 hiring decisions and found that managers who overrode algorithmic resume-screening recommendations frequently produced worse downstream hires than the algorithms themselves. The relevance to a recruiter's daily workflow: when hiring managers reject candidates that structured screening surfaces, the override is often the source of the noise — not the algorithm.

Similarly, research in Noise: A Flaw in Human Judgment by Daniel Kahneman, Olivier Sibony, and Cass Sunstein (Little, Brown Spark, 2021) documents that unstructured interviews produce inconsistent candidate evaluations across interviewers evaluating the same candidate (see Chapter 24, "Structure in Hiring"). AI interview tools address this by enforcing structure on the parts of screening where structure works.

Step 1: Identify which hiring activities benefit from automation

Not every hiring activity should be automated. The first step is identifying which parts of hiring are operational and which require judgment.

Activities that work well with AI

AI interview tools perform best when evaluation criteria are structured and repeatable. These include initial technical screening, structured behavioral interviews, identity verification, coding assessment proctoring, interview scheduling, first-pass rubric scoring, and candidate ranking against predefined criteria.

The value comes from consistency. Every candidate receives the same experience and is evaluated using the same standards.

Activities that should remain human-led

Some hiring decisions depend heavily on context. These include team-fit conversations, senior leadership hiring, system design discussions, judgment-based evaluations, borderline candidate reviews, offer negotiations, and final hiring decisions.

These areas require interpretation, nuance, and organizational understanding that AI systems cannot reliably replicate.

Step 2: Understand where AI interview tools fail

The biggest risks emerge when organizations automate decisions that should remain human.

Cultural and team-fit assessment

Successful collaboration depends on interpersonal dynamics. An AI system cannot determine whether a candidate will thrive within a particular team environment or work effectively alongside future colleagues.

Senior and staff-level evaluation

At senior levels, the most important signals involve judgment under ambiguity. Organizations hire staff engineers and leaders for decisions that do not fit predefined rubrics. AI interview tools are optimized for structure, while senior hiring often depends on evaluating how candidates operate without it.

Edge-case context

Strong candidates do not always provide conventional answers. Experienced interviewers can recognize when a candidate has approached a problem differently but correctly. AI systems often struggle to distinguish between incorrect answers and unconventional thinking.

Legally consequential decisions

Hiring regulations increasingly require transparency and oversight for AI-assisted hiring. Examples include:

  • New York City Local Law 144 — requires employers using automated employment decision tools to conduct an annual independent bias audit, publish a summary of results, and notify candidates at least 10 business days before use.
  • The EU AI Act — classifies AI systems used for recruitment and candidate screening as "high-risk," requiring providers and deployers to meet obligations including risk management, data governance, transparency to candidates, human oversight, and conformity assessment before deployment.
  • Emerging AI governance frameworks in Illinois (AI Video Interview Act), Maryland, and Colorado.

Any AI-assisted hiring process should include documented human oversight and auditability. Read more in our hiring compliance overview.

Step 3: Create a practical division of labor

Step 1 covered the what — which activities suit AI versus humans. This step covers the how — building that split into a workflow your team can run on Monday morning.

Set explicit thresholds. For example: candidates scoring above the 70th percentile on a structured technical assessment advance to a human technical interview; candidates between the 50th and 70th percentile receive recruiter review before any rejection; candidates below the 50th percentile are auto-rejected only after a bias audit confirms the rubric is not screening out protected groups disproportionately. Sample rubric weights for a mid-level backend role might look like: code correctness 40%, code quality 25%, problem decomposition 20%, communication 15%.

Track completion rate as a leading indicator. Industry benchmarks for asynchronous AI interviews typically fall between 60–75% completion; if yours drops below 60%, candidate experience or instructions need work before you scale.

Guiding principle: AI should expand and standardize the funnel. Humans should make the decisions that close it.

An AI tool that lets a marginal candidate (say, a 65th-percentile score) reach a human interview costs a small amount of interviewer time. An AI tool that rejects a strong candidate creates a missed hire that may never be recovered.

Step 4: Calibrate AI against historical hiring data

Many organizations deploy AI interview tools without validating whether the system would have identified successful employees from the past.

Before implementation:

  • Run historical candidates through the AI evaluation process.
  • Compare AI recommendations against actual hiring outcomes.
  • Analyze discrepancies.
  • Refine scoring rubrics before launch.

If the AI system would have rejected several successful hires, the problem is usually the rubric, not the candidates.

Step 5: Keep humans in the loop

The best AI hiring programs maintain human oversight throughout the process.

Review borderline rejections

Candidates within 5–10 percentile points of the cutoff should receive human review. A short recruiter review can prevent high-potential candidates from being filtered out unnecessarily.

Monitor rubric drift

Hiring requirements evolve over time. Human oversight helps identify when AI evaluation systems begin drifting away from actual indicators of hiring success — for example, if 12-month retention among AI-recommended hires drops below the retention rate of human-screened hires, the rubric needs recalibration.

Maintain escalation paths

Candidates should always have a path to human interaction when needed. Transparency improves candidate experience and strengthens trust in the hiring process.

Step 6: Measure outcomes instead of activity

Many organizations focus on operational metrics such as interviews completed, candidates screened, and time saved. These metrics do not measure hiring quality.

Measure what matters

  • 12-month retention — tracks whether employees remain with the company and succeed over time.
  • Performance reviews — measures whether hires deliver expected business impact.
  • Hiring manager satisfaction — provides direct feedback on candidate quality.
  • Time-to-hire — measures hiring efficiency without sacrificing quality.
  • Candidate completion rates — help identify friction points and candidate experience issues.

Track these against pre-AI baselines so you can identify whether AI-assisted screening is contributing to better hires or just faster ones.

Step 7: Manage candidate experience carefully

Candidate reactions to AI interviews vary significantly.

What candidates often like

  • Flexible scheduling
  • Faster response times
  • On-demand interview completion
  • Reduced scheduling friction

Common concerns

  • Lack of human interaction
  • Difficulty building rapport
  • Concerns about fairness
  • Uncertainty about how responses are evaluated

Organizations should clearly communicate how AI is being used, what is being evaluated, how decisions are made, and when humans are involved. Transparency is increasingly both an operational norm and a regulatory expectation.

Common mistakes when implementing AI interview tools

Most implementation failures follow predictable patterns:

  • Replacing humans too early in the hiring process
  • Using AI as the sole basis for rejection decisions
  • Failing to validate scoring rubrics
  • Measuring efficiency instead of hiring quality
  • Ignoring candidate experience metrics
  • Neglecting bias audits and compliance reviews

Organizations that avoid these mistakes typically achieve stronger hiring outcomes and higher candidate trust.

Where HackerEarth OnScreen fits

The compliance, calibration, and human-in-the-loop requirements above raise an operational question: which platform actually combines structured AI screening with the proctoring and identity verification that bias audits and remote hiring require? HackerEarth OnScreen combines in-depth interviewing, integrated proctoring, and KYC-grade identity verification — a combination no single product has previously offered in this category. The AI handles the structured-screening layer (rubric-based scoring against role-specific criteria your team defines, identity verification, and proctoring signal) so human interviewers focus their time on the later-stage judgment calls Step 1 identified as off-limits to automation.

Frequently asked questions

Are AI interview tools more biased than human interviewers?

AI interview tools apply evaluation criteria more consistently than human interviewers, but they can encode bias if trained on biased historical data. Annual bias audits, as required by NYC Local Law 144, and ongoing human review of borderline rejections are how organizations keep that risk in check.

When should organizations avoid AI interviews?

Organizations should avoid AI interviews for executive search, C-suite hiring, highly specialized roles where the rubric cannot be defined in advance, and any interview stage where judgment under ambiguity is the primary signal being measured.

How can organizations determine whether an AI interview tool is successful?

The clearest measure of success is whether AI-screened hires retain and perform at least as well as human-screened hires over 12 months. Pair that with hiring manager satisfaction surveys and completion-rate benchmarks to get a full picture.

Do candidates dislike AI interviews?

Candidate reaction depends on transparency and optionality. Some candidates appreciate flexibility and convenience, while others prefer human interaction; offering an opt-in human touchpoint and clearly explaining how the AI evaluation works closes most of the experience gap.

What compliance considerations apply to AI interview tools?

Organizations using AI interview tools must maintain bias audit documentation, candidate disclosures, audit trails, and documented human oversight to meet regulations including NYC Local Law 144, the EU AI Act, and Illinois's AI Video Interview Act.

Key takeaways

  • The Cowgill (NBER, 2018) finding — that human overrides of algorithmic screening produced worse hires across 300,000 decisions — is the single strongest argument for keeping AI in the early funnel and humans in the late funnel.
  • NYC Local Law 144 requires an annual independent bias audit and 10-business-day candidate notification; the EU AI Act classifies hiring AI as high-risk and requires human oversight by law.
  • Calibrate AI tools by running 12–24 months of historical hires through the system before launch; if it would have rejected your top performers, fix the rubric.
  • Set percentile-based escalation thresholds (e.g., review every candidate within 5–10 points of the cutoff) so borderline cases always reach human eyes.
  • Measure 12-month retention and hiring manager satisfaction against pre-AI baselines — not interviews completed.
Human Overrides vs. Algorithm: Hire Quality Outcomes
Source: Cowgill, NBER Working Paper No. 21709, 2018 (downstream hire quality index, illustrative scale based on article claims)

See it in action

Schedule a demo of HackerEarth OnScreen to map which stages of your current hiring workflow can move to AI screening, which must stay human-led, and how to set percentile thresholds and bias audits aligned with NYC Local Law 144 and the EU AI Act before you scale.

When AI Interviews Work and When They Don't: An Honest Breakdown by Role Type and Seniority

When AI Interviews Work and When They Don't: An Honest Breakdown by Role Type and Seniority

AI interviews work well for structured, rubric-driven screening of high-volume and mid-skill technical roles. They fail predictably when evaluation depends on judgment, context, collaboration, or organizational fit.

The honest answer to "when AI interviews work and when they don't" is simple: AI follows the rubric. If the rubric captures what matters for the role, AI interviews generate useful signal. If the role depends on context, judgment, or nuanced decision-making, AI interviews miss what matters most.

This guide is for recruiters, hiring managers, and talent acquisition leaders evaluating where AI interviews belong in the hiring process. It covers what AI interviews are, where they work best, where they fall short, how effectiveness changes by seniority level, and how to integrate them into a modern hiring workflow.

What Is an AI Interview?

An AI interview is a structured screening process conducted through software that asks standardized questions, evaluates responses against predefined criteria, and produces a consistent candidate assessment.

Most AI interview platforms include:

  • Automated questioning
  • Structured scoring rubrics
  • Video or voice interactions
  • Identity verification
  • Proctoring and integrity checks
  • Candidate ranking and reporting

The defining characteristic of AI interviews is consistency.

Unlike human interviewers, who may evaluate candidates differently depending on experience, fatigue, or bias, AI applies the same evaluation framework to every candidate.

The trade-off is straightforward:

  • Greater consistency
  • Less contextual judgment

AI interviews are not bias-free. Like any evaluation system, outcomes depend on training data, scoring logic, and rubric design. The goal is not eliminating bias entirely but reducing variability and improving consistency.

When AI Interviews Work

High-Volume Technical Screening

This is the strongest use case for AI interviews.

When organizations need to evaluate hundreds or thousands of candidates, consistency becomes more important than depth.

AI interviews can apply identical evaluation criteria across large applicant pools while significantly reducing recruiter workload.

Organizations conducting large-scale engineering recruitment often use AI interviews to maintain calibration across thousands of applications.

Campus and Early-Career Hiring

Campus hiring creates ideal conditions for AI screening:

  • Large candidate volumes
  • Clearly defined skill requirements
  • Standardized evaluation criteria
  • Structured hiring workflows

For organizations hiring hundreds or thousands of graduates annually, human-only screening is often impractical.

Mid-Level Individual Contributor Roles

AI interviews perform well for roles where expectations are well understood and measurable.

Examples include:

  • Backend Engineers
  • Frontend Developers
  • Data Analysts
  • QA Engineers
  • DevOps Engineers

For these positions, structured evaluation often produces reliable screening outcomes before human interviews begin.

Hiring Pipelines Impacted by Scheduling Delays

Interview scheduling remains one of the biggest causes of candidate drop-off.

AI interviews allow candidates to complete screening immediately rather than waiting days for recruiter availability.

For global hiring teams operating across multiple time zones, reduced scheduling friction can significantly improve candidate experience and pipeline speed.

When AI Interviews Don't Work

Senior and Staff-Level Engineering Roles

At senior levels, technical competence is only part of the evaluation.

Organizations need to assess:

  • Decision-making under uncertainty
  • System design trade-offs
  • Stakeholder management
  • Technical leadership
  • Long-term architectural thinking

These capabilities are difficult to evaluate through a fixed rubric.

AI interviews can validate technical fundamentals but should not replace senior-level technical discussions.

Leadership and Executive Hiring

Leadership hiring depends heavily on:

  • Strategic thinking
  • Organizational fit
  • Vision
  • Influence
  • Team-building ability

These qualities are highly contextual and difficult to standardize.

AI interviews should generally not serve as a primary evaluation mechanism for director, VP, or executive roles.

Culture-Driven Hiring

Some hiring decisions are fundamentally conversational.

Examples include:

  • Founding engineers
  • Startup leadership hires
  • Early-stage team members
  • Strategic partnership roles

In these situations, relationship-building and mutual assessment matter more than standardized scoring.

Live Collaboration Assessments

If collaboration is central to the role, collaboration should be part of the interview process.

Examples include:

  • Pair programming
  • Design reviews
  • Team problem-solving sessions
  • Cross-functional workshops

AI interviews can assess baseline competency, but live interaction remains essential.

Highly Contextual Non-Technical Roles

AI interviews struggle when success depends on:

  • Relationship management
  • Negotiation
  • Executive presence
  • Network-building
  • Client judgment

Roles such as enterprise sales, partnerships, executive recruiting, and senior customer success generally benefit more from human-led evaluation.

AI Interview Effectiveness by Seniority Level

The pattern across technical hiring is remarkably consistent.

Entry-Level and Fresher Hiring

AI interviews work extremely well.

Characteristics:

  • High applicant volume
  • Stable evaluation criteria
  • Structured skill requirements

Recommended approach:

AI Interview → Human Validation → Offer

Mid-Level Individual Contributors (L3–L4)

AI interviews work effectively as a first-round screen.

Recommended approach:

Assessment → AI Interview → Human Technical Interview

Senior Individual Contributors (L5)

AI interviews provide useful signal but should not determine hiring outcomes.

Recommended approach:

Assessment → AI Interview → Senior Panel Interview

Staff and Principal Engineers (L6+)

AI interviews offer limited value.

Evaluation should focus on:

  • Architecture
  • Decision-making
  • Leadership
  • Influence

Recommended approach:

Structured Human Panel Interviews

Managers and Directors

Behavioral interviews, leadership evaluations, and reference checks provide stronger signal than AI screening.

VP and Executive Roles

AI interviews are generally not recommended.

What This Means for the Hiring Process

The most common mistake organizations make is treating AI interviews as an all-or-nothing decision.

AI interviews are most effective when positioned as a stage within the hiring funnel rather than a replacement for human evaluation.

For many technical hiring programs, the ideal sequence is:

Skills Assessment → AI Interview → Human Technical Interview → Final Panel

In this model:

  • Assessments validate technical skills
  • AI interviews provide structured screening
  • Human interviews evaluate judgment and collaboration
  • Final panels determine overall fit

This approach combines scalability with human decision-making.

Frequently Asked Questions

Are AI Interviews Fair?

AI interviews generally provide more consistent evaluations than human screeners because every candidate receives the same questions and scoring criteria.

However, fairness depends heavily on:

  • Question design
  • Rubric quality
  • Calibration processes

How Do AI Interviews Handle Candidates Using AI Tools?

Modern platforms combine:

  • Identity verification
  • Proctoring
  • Screen monitoring
  • Dynamic follow-up questions

While no system is perfect, these measures significantly increase assessment integrity.

Can AI Interviews Replace Human Interviewers?

No.

AI interviews can replace or augment first-round screening for many technical roles.

They cannot replace human judgment for senior, leadership, or highly collaborative positions.

What Is the Biggest Risk?

False negatives.

Candidates with unconventional backgrounds or problem-solving approaches may not fit expected scoring patterns despite having strong potential.

Organizations should periodically audit rejected candidates to ensure the screening process remains effective.

How Long Should an AI Interview Be?

For technical screening, 30–45 minutes is typically optimal.

Interviews longer than 60 minutes often increase candidate drop-off without improving signal quality.

When Should Organizations Avoid AI Interviews Entirely?

Avoid AI interviews for:

  • Staff and Principal Engineers
  • Leadership Roles
  • Executive Hiring
  • Culture-Critical Positions
  • Low-volume hiring where personalized evaluation is feasible

Key Takeaways

  • AI interviews perform best for high-volume, structured technical hiring.
  • Campus hiring and mid-level technical roles are ideal use cases.
  • Senior, leadership, and culture-driven roles require human judgment.
  • The practical transition point is typically around the L5 level.
  • AI interviews should complement human decision-making, not replace it.
  • The primary value comes from consistent screening and reduced recruiter workload.

Next Steps

If you're evaluating where AI interviews fit within your hiring process, start by identifying which roles depend primarily on measurable skills and which depend on judgment, collaboration, and leadership.

The strongest hiring funnels combine assessments, AI screening, and human interviews in a sequence that matches the role being hired.

Pre-Employment Coding Tests: Recruiter's Guide 2026

Pre-Employment Coding Tests: Recruiter's Guide 2026

The U.S. Department of Labor estimates a bad hire costs at least 30% of the employee's first-year salary. For a $130,000 senior engineer, that is $39,000 before you account for lost productivity, team disruption, and the weeks spent restarting the search. Most of that risk traces back to a broken screening process: resumes that inflate skills, unstructured interviews that measure confidence over competence, and hiring decisions made on instinct.

Pre-employment coding tests solve this directly. A well-designed pre-employment coding test gives every candidate the same objective problem, evaluates the result against consistent criteria, and produces a defensible, data-backed signal before anyone has spent an hour of interview time.

This guide is for recruiters, hiring managers, and engineering leads building or refining a technical hiring process. It covers what coding tests are, how to choose the right format, how to design assessments that actually predict job performance, how to protect integrity, how to evaluate results fairly, and how to avoid the mistakes that turn a good testing program into a candidate drop-off machine. Note: this is a practical implementation guide focused on screening workflow; it does not exhaustively cover EEOC legal review, accessibility accommodations under the ADA, or multi-region data privacy compliance (GDPR, India DPDP, etc.). Consult qualified counsel for those areas.

What is a pre-employment coding test?

A pre-employment coding test is a standardized assessment given to job candidates before the live interview stage to objectively measure programming skills, problem-solving ability, and code quality. Candidates receive coding challenges on an assessment platform, write code in a real or simulated IDE, and results are scored automatically or reviewed by engineers against consistent criteria.

What every format shares is that it creates a concrete, reproducible record of what a candidate can actually do, rather than what they claim on a resume.

Types of coding tests used in hiring

The five main formats each serve different evaluation goals. Algorithmic coding challenges test data structure and problem-solving fluency under timed conditions. Project-based take-home assignments evaluate real-world code quality, architecture thinking, and documentation. Multiple-choice tests screen foundational language knowledge at high volume. Live coding interviews let interviewers observe how a candidate thinks in real time. Pair programming assessments evaluate collaboration alongside technical ability. Each format is covered in full in Step 2.

When pre-employment coding tests are not the right tool

Pre-employment coding tests are powerful for high-volume technical screening, but they are not universally appropriate. For highly specialized research roles (e.g., applied ML researchers, compiler engineers, cryptography specialists), a standardized challenge rarely captures the depth of the work, and a portfolio review plus deep technical conversation is typically a stronger signal. Internal transfers with documented performance histories generally should not be re-screened with the same assessment used for external candidates. Niche language experts or open-source maintainers with verifiable public portfolios may also be better evaluated on the artifacts they have already shipped. Scoping when not to test is part of designing a defensible hiring process.

Why pre-employment coding tests are critical for technical hiring

The problem is not a shortage of applicants: it is a shortage of reliable signal. Engineering roles take an average of 62 days to fill globally, according to Workable's 2024 benchmarking data, and roughly 70% of tech recruiters say they consistently receive unqualified applicants for every technical role they post, according to industry reporting from DevSkiller. Without a structured pre-hire coding challenge, teams discover skills gaps during live interviews, which is the most expensive point in the funnel to find out a candidate cannot do the job.

The research supports this directly. Schmidt and Hunter's 1998 meta-analysis, and the updated analysis by Schmidt, Oh, and Shaffer (2016), found that work sample tests have a validity coefficient of .33 to .54 for predicting on-the-job performance, substantially higher than education (.10) or years of experience (.18). A coding aptitude test is, by design, a work sample test. According to TestGorilla's 2025 State of Skills-Based Hiring report, roughly 85% of employers now use some form of skills-based hiring, up from 73% in 2023. The question is not whether to use coding tests. It is how to use them effectively.

Predictive Validity of Hiring Selection Methods
Source: Schmidt, Oh & Shaffer (2016); Schmidt & Hunter (1998)

Step 1: Define the role requirements and testable skills

The most common reason a pre-employment coding test fails to predict job performance is that it tests the wrong things, and that is entirely preventable if you start with a job analysis rather than a question library.

Work backward from what the engineer will do in their first 90 days. Identify must-have skills, where a gap disqualifies the candidate regardless of everything else, and distinguish them from nice-to-have skills that can be learned on the job. Map skills to test formats based on what each format can actually measure: algorithm design for backend roles, DOM manipulation for frontend engineers, API integration scenarios for full-stack developers. System design belongs in the live interview, not a pre-employment skills testing stage.

A skills matrix structures this before you build anything:

SkillPriorityTest FormatDifficulty LevelPython data structuresMust-haveAlgorithmic coding challengeMidREST API designMust-haveProject-based taskMid-seniorSQL query optimizationMust-haveCoding challengeMidGit workflowNice-to-haveMCQFoundationalSystem architectureNice-to-haveLive interviewSenior

The matrix forces alignment between engineering and recruiting before the test is built. It is also your first line of legal defense: tests traceable to specific job tasks are far easier to defend under EEOC scrutiny than tests assembled from a generic question bank.

Step 2: How to choose the right type of coding assessment

A pre-employment coding test that works well for junior backend hiring will actively mislead you when evaluating a senior full-stack candidate, and this is one of the most common and preventable process mistakes in technical hiring.

Multiple-choice questions (MCQs)

MCQs are useful as a first-pass filter for high-volume junior pipelines, but answering a multiple-choice question about recursion is not the same as writing a recursive function. Use them to screen out candidates who lack basic fluency before they invest time on a coding problem. Never use them as a standalone technical skills evaluation.

Algorithmic coding challenges

Algorithm tests are the most common format for backend and infrastructure roles, and the most misused. The well-documented limitation is that LeetCode-style challenges favor candidates who have practiced competitive programming, and senior engineers with real-world experience frequently underperform relative to their actual capability. Use algorithmic tests as one signal, not the deciding one.

Project-based and take-home assignments

Take-home assignments produce the richest signal of any pre-hire coding challenge format because reviewers can see how a candidate structures a solution, handles edge cases, and documents their thinking. The tradeoff is that candidates with competing offers will not complete an assignment that feels open-ended or excessive. Keep scope tight, share the evaluation criteria upfront, and cap the expected time at two to four hours.

Live coding interviews

Live coding is best reserved for final-round evaluation, where observing thought process and debugging behavior in real time is worth the scheduling cost. Some strong engineers simply perform poorly when watched, so use this as a late-stage filter, not an early screen.

Pair programming assessments

Pair programming works well for collaboration-heavy teams and senior roles where working style matters as much as raw output. Scheduling complexity limits scalability, which makes it practical mainly for final-round or specialized role evaluation.

Assessment type comparison

Assessment TypeScalabilityRealismCandidate ExperienceEvaluation EffortBest ForMCQHighLowLow frictionLowHigh-volume, foundational screeningAlgorithmic ChallengeHighMediumMixedLow (automated)Backend, infrastructure, junior-to-mid rolesProject / Take-HomeLow-mediumHighHigh frictionMedium-highMid-to-senior, code quality focusLive CodingLowHighVariableHighFinal-round, process observationPair ProgrammingLowVery HighPositiveHighSenior, team-fit evaluation

Step 3: Select a coding assessment platform

Platform selection has downstream consequences for every hire you make, and a weak choice here creates friction at exactly the points where hiring speed matters most.

When evaluating coding assessment platforms, focus on criteria that are independent of any specific vendor: does the question library cover the languages and frameworks you actually hire for, or will your team spend weeks authoring custom content? Does the platform integrate natively with your ATS (Greenhouse, Lever, Workday, iCIMS), or will recruiters re-key candidate data? What signals does the proctoring system surface, and can you interpret them quickly when reviewing flagged sessions? Can you customize scoring rubrics for proprietary questions, or are you locked into the vendor's defaults? Does the reporting let hiring managers compare candidates against a cohort, or only against a static score? Capterra's 2024 candidate research, summarized in their job seeker survey coverage, found that around 58% of candidates used AI tools to complete assessments — making proctoring signal quality a load-bearing criterion, not a checkbox.

Different platforms make different tradeoffs here. Codility is widely cited for clean candidate-facing UX and a strong focus on engineering-team workflows. HackerRank has one of the deepest public question libraries and a large developer community footprint, which helps with content variety. TestGorilla's strength is breadth: multi-skill assessments that extend beyond pure coding into cognitive, personality, and role-fit testing, which suits generalist hiring.

HackerEarth, positioned as a skills intelligence platform, takes a different approach on integrity signal: rather than surfacing raw proctoring logs and asking recruiters to interpret them, the platform consolidates plagiarism, environment, and behavioral signals into a single per-candidate integrity output that recruiters can act on without forensic review — a tradeoff competitor platforms often leave to the reviewer. HackerEarth covers 40+ programming languages, supports 1,000+ skills across role types, and offers role-specific templates for frontend, backend, data science, and DevOps so hiring managers do not start from a blank slate. ATS integrations with Greenhouse, Lever, iCIMS, and Workday route results into the candidate record automatically. It is used by 500+ global enterprises including Google, Microsoft, Elastic, Flipkart, and Brillio.

Step 4: Design a fair, effective, and job-relevant pre-employment coding test

Platform selection is the infrastructure decision. Test design is the content decision, and most well-resourced technical hiring programs still underperform here.

Set the right duration

Forty-five to 90 minutes is the optimal range for a timed online pre-employment coding test. Below 45 minutes, complex challenges cannot be evaluated meaningfully. Beyond 90 minutes, completion rates drop sharply among senior candidates with competing offers. Take-home projects are the exception: two to four hours is acceptable when scope is explicitly defined and candidates know what "done" looks like.

Calibrate difficulty to the role

Testing a senior engineer on problems they solved in year one is the equivalent of asking a seasoned chef to boil water to prove they can cook. Define difficulty bands before building the test: Junior (0-2 years) needs language fundamentals and basic data structures; Mid-level (3-5 years) needs applied problem-solving and API integration; Senior (6+ years) needs system design judgment, code review, and performance optimization.

Mix question types strategically

One to two MCQs combined with one to two coding challenges produces a more accurate signal than either format alone. MCQs identify candidates who lack basic fluency before they invest time on a harder problem; coding challenges surface gaps that MCQ performance does not predict.

Reduce bias in test design

This is the area where most competitor guides stop short, and it is the most consequential one for both fairness and legal compliance. Avoid questions that require knowledge of specific cultural contexts, idioms, or domains that favor particular educational backgrounds. The test should measure coding ability, not cultural familiarity.

The EEOC's May 2023 technical guidance makes explicit that adverse impact and job-relatedness requirements under Title VII apply to algorithmic and AI-assisted selection tools. Any test producing a disproportionate pass or fail rate for a protected group must be demonstrably job-related and consistent with business necessity, or it creates legal liability.

Practical steps: document the link between each question and a specific job task before publishing the test; apply the four-fifths rule (if a protected group's pass rate falls below 80% of the highest-performing group's pass rate, investigate); and do not use LeetCode performance as a proxy for software engineering ability. Research, including work summarized in the ACM's review of technical interview practices, suggests the correlation between competitive-programming performance and real-world engineering effectiveness is weaker than commonly assumed. These tests can also systematically disadvantage candidates from non-traditional backgrounds who are strong practical engineers.

Step 5: Implement anti-cheating and proctoring measures

Skipping proctoring is not a neutral decision heading into 2026: it is a decision to accept that a meaningful portion of your results cannot be trusted. Capterra's 2024 candidate research reported that around 58% of candidates used AI tools to complete assessments, and the Identity Theft Resource Center's 2024 trends report documented that application fraud rose more than 118% between 2023 and 2024.

Effective remote proctoring for online assessments layers multiple signals: plagiarism detection that compares submissions against known published solutions and other candidates in the cohort, browser lockdown to block access to AI tools and search engines, webcam monitoring using computer vision rather than manual review, randomized question pools so candidates cannot share answers, and IP tracking to flag submissions from the same device.

The balance with candidate trust is real. Communicate proctoring measures in the assessment invitation, explain why they exist, and calibrate oversight to the role's sensitivity. Senior engineers view intrusive monitoring as a signal about organizational culture, and the employer brand damage from that reaction is harder to undo than the integrity risk you were trying to prevent.

Step 6: Evaluate results and make data-driven hiring decisions

A test score is not a hiring decision, and teams that treat it as one will make the same mistakes as teams that never ran the test at all.

Automated scoring vs. manual review

Automated scoring removes the variance that comes from different engineers reviewing the same submission with different standards. Rubric-applied evaluation is more consistent across candidates than human-led screens and does not vary by interviewer mood or fatigue, where variable naming style and code structure conventions can unconsciously influence how a reviewer rates competence. For mid-to-senior roles, combine automated scoring for correctness and efficiency with targeted manual review of code architecture and readability.

Build a scoring rubric

Every candidate should be evaluated against the same weighted criteria. A sample rubric:

CriterionWeightWhat to EvaluateCorrectness40%Does the code produce the right output across all test cases, including edge cases?Efficiency25%Is the time and space complexity appropriate? Are obvious optimizations made?Code Quality20%Is the code readable? Are naming conventions consistent? Is the logic well-structured?Edge Case Handling15%Does the candidate account for null inputs, boundary conditions, and unexpected states?

Set benchmarks and pass thresholds

An arbitrary cutoff like "everyone above 70% passes" is not a benchmark, it is a guess. Use percentile-based cutoffs calibrated to your actual candidate pool: the top 30% of submissions for a role type is a more defensible threshold than a static score. HackerEarth's reporting supports cohort-level comparisons so pass thresholds can reflect real performance distributions rather than guesses.

Avoid common evaluation pitfalls

Speed is not skill. A candidate who solves a problem in 30 minutes is not necessarily better than one who takes 60; penalize only when completion time indicates the candidate could not arrive at a solution, not because they were slower than average. A valid but unconventional solution is also not a failure: if the code is correct, efficient, and readable, the approach the candidate used tells you something positive about how they think.

Step 7: Communicate clearly with candidates before, during, and after

The developers you most want to hire have options, and a confusing or silent assessment process is enough to lose them to a competitor who treats communication as part of the job.

Provide timely, constructive feedback

Talent Board's CandE Benchmark Research consistently shows that candidates who receive feedback (even a rejection) rate the employer more favorably than those who receive nothing. In a market where roughly 61% of job seekers report being ghosted after an interview, per Greenhouse's 2024 candidate experience research, any communication at all is a differentiator. A note indicating the general area where a candidate did not meet the bar protects the employer brand and keeps the door open for future applications.

Set clear expectations for the interview stage

Tell shortlisted candidates what the live interview will cover before they arrive. The assessment invitation itself should include the expected duration, what to have ready, a description of what skills are being tested, the proctoring measures in use, the submission deadline, and a contact for technical issues.

Step 8: Integrate pre-employment coding tests into your hiring workflow

A pre-employment coding test produces its full value only when it sits in the right place in the funnel, and that place is stage two, after the resume screen and before any engineer's time is committed.

A typical technical hiring funnel with coding tests placed correctly:

ATS integration makes this practical at scale. Platforms that connect natively with Greenhouse, Lever, and Workday trigger assessment invitations automatically, route results back into the candidate record, and apply pass/fail logic without manual recruiter intervention. The long-term refinement loop matters as much as the initial setup: track which questions correlate with strong 90-day performance reviews and retire the ones that do not predict what you need them to predict. For deeper guidance on building this end-to-end, see HackerEarth's resources on skills-based hiring and technical interview design.

Common mistakes that undermine your coding assessments

Most assessment programs fail not because the platform was wrong but because of predictable process errors that go unexamined.

Testing skills that are irrelevant to the actual job. Every question should trace back to the skills matrix from Step 1. A puzzle that has nothing to do with the day-to-day work filters for interview prep performance, not job readiness, and strong candidates who recognize the disconnect opt out.

Making the test too long. Senior developers with multiple offers will not complete a three-hour screen before they have had any meaningful interaction with the company. Completion rates drop sharply past 90 minutes, and over-length tests produce more drop-off, not more signal.

Using a one-size-fits-all assessment for all roles and levels. A test calibrated for a mid-level backend engineer is wrong for a junior frontend hire and wrong again for a senior DevOps lead. Each role requires its own skills matrix and difficulty calibration.

Relying solely on automated scores without context. A candidate who scores 68% on a well-designed test may be significantly more capable than one who scores 75% on a poorly designed one. Scores are inputs to a decision, not the decision itself.

Not validating the test for adverse impact or job-relatedness. Failing to document the link between test content and job requirements, or failing to monitor pass rate disparities across demographic groups, creates Title VII liability under the EEOC's Uniform Guidelines on Employee Selection Procedures. This is the most consistently overlooked area in pre-employment testing programs.

Failing to iterate on test design. A coding test that was well-designed 18 months ago may now have its questions circulating on developer forums. Track the correlation between assessment scores and 90-day performance reviews; the questions that are no longer predicting performance are the ones to retire.

Frequently asked questions about pre-employment coding tests

Is a pre-employment coding test the same as a LeetCode-style interview?

No, and conflating the two is one of the most common reasons hiring programs underperform. A LeetCode-style problem is one narrow input — competitive-algorithm fluency under time pressure. A well-designed pre-employment coding test is broader: it can include work-sample tasks, debugging exercises, API integration scenarios, or framework-specific problems that resemble the actual job. The "test" is the design philosophy, not a specific question format, and the most effective programs deliberately move away from pure algorithm puzzles for non-algorithm-heavy roles.

How long should a pre-employment coding test take?

Forty-five to 90 minutes is the optimal range for a timed coding challenge; take-home projects should be capped at two to four hours with clearly defined scope. Senior candidates in particular will abandon anything that feels like an unreasonable time investment before a first interaction with the company.

Are coding tests a reliable predictor of job performance?

Work sample tests have a validity coefficient of .33 to .54 for predicting on-the-job performance according to Schmidt and Hunter's 1998 meta-analysis (and the 2016 update by Schmidt, Oh, and Shaffer), which is substantially better than education (.10) or years of expert

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