Inside Netflix Engineering: CTO Elizabeth Stone on Autonomy, Live Streaming, and Unusual Responsibility

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Overview

What is it like to work as a software engineer at Netflix, and how does a company of its size let engineers make major decisions without layers of approval? In this conversation, recorded at Netflix's Los Gatos offices, the host of The Pragmatic Engineer asks Netflix CTO Elizabeth Stone about the company's engineering culture. Stone's central argument is that Netflix's autonomy, lack of process, and high talent bar are not goals in themselves but means to excellent work. The discussion covers how the company built live streaming in about 18 months, what went wrong along the way, how it handles performance without formal reviews, and where it is finding value in AI tools.

30 min read

The scale behind the streaming app

Stone begins with the scale of the operation, which she says is probably larger than people realize. People in her personal life often ask how many engineers it can really take to build the Netflix product. Her answer is that making the member experience seamless, and ideally invisible, already takes a lot of engineers, but the tech organization also builds much more. It builds tools and products for studio productions, runs Netflix's advertising tech stack, provides developer platform and launch capabilities for games, and supports anything related to commerce: plans, pricing, payments, and partnerships.

Across all of this, Stone says Netflix captures more than a trillion events every day. These come from consumer interactions and from activity across the products and services that support decision-making. She describes the company as "quite a global enterprise at this point."

Technology built for the studio

The host notes that payments and ads are common at large tech companies, but custom software for a production studio is not. Stone calls bringing technology to entertainment "very much part of our superpower." Because Netflix is one of the biggest studios in the world, she says it can look for problems it is uniquely positioned to solve for productions.

Her main example is Netflix's media production suite. It replaced what Stone describes as a fairly antiquated, slow, and expensive way of moving media files between creative teams around the world. In her example, a production shoots somewhere in Europe while a reviewer in Los Angeles watches the daily footage. The files travel to Los Angeles, the reviewer adds notes, and the notes travel back in time for the next day of shooting. Netflix also builds other tools for tracking how productions are progressing.

Stone also mentions Scanline and Eyline, a visual effects studio Netflix acquired a few years ago. According to Stone, it does cutting-edge research and technology work on data capture and visual effects, and on techniques that bring productions to life in ways standard camera technology cannot easily achieve.

The host asks about the engineering challenges involved. Stone points first to scale: hundreds or thousands of productions may be in progress at once, and their media files are especially large, complex, and hard to move. That makes the cost of storage, compute, and data transfer a real concern. Latency requirements depend on the use case. Footage reviewed the next day can tolerate delay, but media for live productions must move essentially instantaneously. The other challenge she stresses is quality. Producing very high-quality images and video, both for the content itself and for how it is promoted on the service, creates many engineering problems of its own.

Open Connect: Netflix's own delivery network

Stone then turns to Open Connect, Netflix's content delivery network, which she calls extremely unique. She describes building it as a big bet Netflix made more than ten years ago. By her account, Open Connect now spans 6,000 locations in more than 175 countries. It places local copies of films, TV shows, and games close to members so they get low latency and high quality wherever they press play. Netflix integrates with internet service providers so the content can travel the "last mile" to a phone, TV, or laptop.

The host observes that engineers at most other companies would treat a CDN as a black box bought from a vendor, while Netflix engineers build it themselves. Stone agrees and calls Open Connect an incredible head start whenever Netflix moves into new content types. It became a strategic advantage when the company expanded into live and games, especially cloud-streamed games, and Netflix is extending it to deliver these new types of content.

"Pitch to play": engineering across the whole content lifecycle

Stone says Open Connect is really the end of a long, integrated lifecycle that Netflix has engineered from start to finish. Internally this is sometimes called "pitch to play." The lifecycle begins when someone pitches a title and the content team greenlights it. Data science and engineering teams support those programming decisions. Tech teams then support the production of the content through tools like the media production suite, including transferring files for quality review and checking alignment with the creative vision.

Once a title is ready, it moves through other pipelines. These check whether the promotional assets are ready, whether Netflix can recommend the title to the right audiences, and how the files should be encoded for delivery through Open Connect. Stone argues this is unusual because most companies have not built such a pipeline themselves. The host compares it to a CI/CD pipeline, and Stone suggests imagining that pipeline "times thousands," since it follows the entire cycle of bringing content to members.

Engineers, not top-down architecture, drive the system

The host asks whether such a long pipeline makes Netflix rigid. Stone says this is where Netflix's culture matters. According to Stone, much of Netflix's engineering systems, products, and tools were designed by individual contributors. Innovation came from within teams, not from the top down. Teams have substantial autonomy and rely on local judgment. Stone credits this with producing the end-to-end system, and with letting Netflix rearrange its "puzzle pieces" when new needs appear.

Live is her example. Many components already existed for film and TV on demand. When Netflix moved into live, engineers had to rethink content delivery for live's requirements. They started from what already existed and made their own decisions about how to evolve it. Stone contrasts this with an approach where someone says "let me draw the architecture for you" and everyone builds toward it.

She acknowledges that this has trade-offs. As the company grows, scale becomes more of a challenge, and Netflix has had to evolve how it builds things so the systems can support that growth. In her view, this flexibility is what lets Netflix engineer for its current needs rather than the needs it had ten years ago.

Building Netflix Live: 18 months to the largest streamed event

The host asks how Live came together and whether it was carefully planned or "yolo." Stone laughs and says it was "not quite yolo." Netflix's first live title was a Chris Rock special, which she believes aired in March 2023. The Jake Paul vs. Mike Tyson fight took place in November 2024, so Stone counts about 18 months from Netflix's first live event to what became the largest streamed event ever.

She says the work happened through urgency, scrappiness, and engineers taking ownership. The fight was originally scheduled for July 2024 and was moved to November because of Tyson's health, which gave the teams a few extra months. Teams from Open Connect, encoding, content production and promotion, and discovery decided who needed to be involved. Stone emphasizes that they self-organized: they wrote their own roadmaps, assigned their own owners, and identified which systems needed to become resilient enough for live. She describes the timeline as incredibly tight.

The event reached 65 million concurrent streams. Stone recalls it as one of Netflix's biggest days ever for signups. By the first couple of undercard fights, viewership had already passed Netflix's expectations for the main event. She describes the launch room in Los Gatos as full of excitement and nervousness, with engineers solving problems in real time "because no one had ever seen scale like that." She says she has never been prouder of the team for figuring out which levers to pull to keep the stream as stable as possible.

The event also had problems. Five weeks later, Netflix had to stream two NFL games on Christmas Day, where Stone says the bar for fans is very high. The team used what it learned from the fight to improve resilience. It worked out how to direct traffic if some markets became bandwidth-constrained and how to use quality levers to optimize the experience. By Stone's account, the NFL games "ended up being flawless."

She summarizes the progression as Chris Rock, then a Love Is Blind failure, then Paul–Tyson with many lessons at scale, then the NFL, and now weekly WWE plus other large events. She credits all of it to teams on the ground. She adds that learning fast does not mean avoiding failure; it means learning quickly from failures, iterating, and improving. She says she has seen the same pattern when Netflix built its own ads tech stack, launched games, and shipped its new TV UI.

Inside the control room

The host asks what the control room looked like, guessing it was full of dashboards. Stone says even the dashboards were brand new. The data science and engineering teams built them together for the event. They tracked core quality-of-experience metrics such as time to render, app start time, and rebuffer rates. She says rebuffers were the metric that started to climb during the Paul–Tyson fight.

About a hundred people were on site. Stone sat in a room with roughly 30 or 40 engineers and data scientists, working on laptops and makeshift screens. Everyone had a wired internet connection to avoid Wi-Fi risk, and VPN backups were ready. A launch commander wore a headset connected to the production truck. Stone stresses that it was not streamlined, not perfect, and not like the polished launch rooms she imagines most live productions have. When a metric turned red, the team created makeshift Google Meet rooms so small groups could triage. For each area, such as Open Connect, playback, or discovery (whether people could find the title at all), specific people were named as informed captains or decision-makers in the launch plan. She says the plan grew to 40 or 50 pages of if-then statements.

Stone jokes that she feels she "lost 10 years of my life in that one night." It was stressful, and she had nothing to do on a keyboard; her role was to support the team and trust it to make decisions. She says the NFL games, the Canelo–Crawford fight, and WWE are now far more sophisticated in resilience, metrics, dashboards, and visibility. The early events were very human-driven, and she says that is where many of the lessons came from. She tells her team it is rare to work at a mature company and still build something truly from scratch: to anticipate what could go wrong, prepare for it, and stay calm under pressure when something happens.

After the fight: learning without a mandated process

The host notes that the team had prepared extensively and still had problems with both Love Is Blind and the Paul–Tyson match, and asks how formal the follow-up was. Stone says Netflix does hold blameless post-mortems and retros, and that the learnings are more interesting than who did what wrong. But the process is not rigid. It happens organically and is led by the people closest to the work, who feel strong accountability for reflecting on what went well and what could be better.

She describes the days after the fight as a complicated mix of emotions. The team was celebrating the biggest live stream ever, a company willing to take such a big swing, and systems that did not collapse at 20, 30, and 40 million concurrent streams. If someone had told her beforehand that there would be 65 million, she says, she would have predicted it would not go well. Still, there were hiccups, and Netflix always wants to deliver a great member experience.

Stone says she was awake all night thinking about next steps, with only five weeks until the NFL. In the morning, she found memos the team had already written: what they observed, what could be improved, and what to prioritize immediately. One focus was traffic direction under congestion. The team compared what the algorithms had actually done with what they should do when congested, and looked at how the system could fall back or degrade gracefully under that kind of stress. Stone says none of this could have been designed before seeing how the systems behaved live.

She links this to a phrase in Netflix's culture memo, being "unusually responsible." In her view, it comes from high talent density and from treating people like adults: they get a lot of autonomy and in return they own the outcomes. She sees her own role as offering input and asking questions so she can understand and accurately represent what happened. A leader almost never has to tell the team what to do next.

Guardrails since Live: tiers, testing, and quiet periods

The host asks how many processes are mandated globally, such as required code reviews, feature flags, sign-offs, or CI checks that cannot be overridden, and how many are left to teams. Stone says a lot is left to teams and individual engineers, including early-career engineers. She points back to when Netflix introduced Chaos Monkey. The idea that each engineer is responsible for understanding how and when their system will break, and for detecting and recovering quickly, became a core part of the culture that Netflix has kept.

She describes Live as the dividing line. Before Live, the company had many years of experience with on-demand video. Teams could take smart risks and decide for themselves how much testing and resilience work they needed, backed by strong on-call and support teams. Live raised the stakes, because Netflix cannot be temporarily down during an event while it fixes a problem. Stone admits this was scary at first.

Netflix responded by introducing guardrails. Applications in the critical path for live, especially tier 0 and tier 1 services, face a higher bar for testing so they are ready for the stress of a live event. A central engineering team shares guidelines. Stone argues this actually gives teams less process: if a team meets the guidelines and completes the testing, it does not have to enter a quiet period during a live event. If it has done end-to-end testing, it understands its dependencies well enough to plan for failure. None of this, she says, is a structured gate like a mandatory code review or a checklist that blocks deployment. Netflix also has quiet periods over the year-end holidays, which she calls pretty common, and some "rules of the road" around live events.

The host summarizes the approach as focusing on the impact of each system rather than on process. Stone agrees and says these tools were new with Live. Live required more structure because it was new, because it was riskier, and because it touches so many teams. A live signal travels from the camera to the production truck, then to the origin or cloud, and then to the CDN, with many systems talking to each other in real time. Until Netflix was confident it understood those connection points, it wanted more guidelines, which is when it introduced the tiering system and the rules about who joins quiet periods. Stone says many of these constraints have since been relaxed. Netflix prefers fewer constraints because they slow down teams whose work has nothing to do with Live, and it does not want to slow the rest of the business for one priority.

Talent density and the arrival of levels

The host points out that Netflix could work this way partly because of its high hiring bar, and notes that for its first 25 years or so, Netflix's only engineering level was senior software engineer. Stone says she is still amazed by Netflix's talent density. Before joining a little over five years ago, she had not quite believed it.

In her view, the elements of the culture, including talent density, "no rules," little process, and "context, not control," are all means to excellent work, not ends in themselves. Operating for so long without levels, rules, or process sent people a message: we expect a lot of you. She calls it a very human reaction to rise to that expectation. The best people thrive with high autonomy and high accountability and are not distracted by what might otherwise surround them.

Keeping this up while growing from a hundred to a thousand to several thousand people requires what she calls "scaffolding." Netflix no longer has a single level. Not every role needs 10, 15, or 20 years of experience. Some are a good fit for recent graduates or people with a couple of years of experience, and those people should have different expectations and compensation. Stone says Netflix previously lacked even the vocabulary to talk about building a team with a broader range of experience. Levels also brought IC and management pathways and defined expectations at each level.

Stone emphasizes that these pathways cover cultural behavior as well as skills. Do you lift up the people around you? Do you deliver excellence and accountability? Do you show selflessness, good judgment, and a focus on what is best for Netflix? She cites several engineering principles. One is building for the future teams who will thank you for your work, which means not taking shortcuts and building high-quality, durable products. Another is "think globally, act locally": considering the wider effects on the tech organization and on Netflix when making local decisions. Her personal favorite is "yearn to learn," which she describes as a memeified way of saying be curious and ask whether you are solving the right problem in the right way. She also warns about incentives that push people to do what benefits themselves rather than their team or the company. Netflix tries to discourage this and to celebrate selfless, less visible work, which she believes keeps attracting and retaining the best people.

No formal performance reviews, and the keeper test

The host recalls performance review season as a month-long distraction every six months when they were a manager. Stone says Netflix has no formal performance reviews, which is probably the first unusual thing. There are no rating calibrations of the "meets / exceeds" kind she has seen elsewhere. Netflix still thinks carefully about feedback, performance, and expectations.

The foundation is meant to be continuous, timely, candid feedback, which Stone admits is "easier said than done." It requires trust and deep relationships, and it includes positive feedback as well as criticism. If people live the culture well, giving and receiving feedback should feel normal every day, with no need to wait for a cycle.

Around that sit several formal touch points. The first is an annual 360 process, which Stone calls a safety net. People request feedback from colleagues, the feedback goes directly to the individual, and each person reviews the themes with their manager. It is framed as feedback for improvement, not as an evaluation. The second is an annual compensation review based on Netflix's "personal top of market" philosophy. Managers consider each person's impact, skills, contributions, and value to Netflix and in the market. Stone says this has "a performance flavor" but is not a performance review. The third is promotion evaluation, which happens a couple of times a year and collects feedback for decisions such as moving from level five to level six. Stone argues these touch points together feel more constructive and actionable than typical review structures.

The approach demands a lot of manager attention and judgment, so Netflix adds checks and balances. As head of the tech organization, Stone reviews who is being promoted and how many, the themes in 360 feedback, and where compensation is landing across teams. Netflix also gives managers substantial support when they make keeper test decisions.

She explains the keeper test as a manager asking whether a person truly meets the expectations of the role and what the business needs. She stresses that it works in both directions. Employees ask whether they want to stay, whether the work excites them, and whether their manager is helping them grow. An employee can also use it to ask their manager directly how they are doing and whether there is feedback they have not yet heard. Ideally, she says, this all happens as part of normal business.

Why engineers stay or leave

The host cites data from SignalFire comparing tech companies' talent bar with retention, in which Netflix appears in the top corner: high-talent engineers were the least likely to leave. Stone says she is glad to hear it but that Netflix has to keep earning it.

In her view, people leave when their work does not give them enough challenge and fulfillment, or when they do not feel adequately recognized. No company can guarantee that, but she believes Netflix gives people many chances to solve hard problems with real agency, without heavy rules or top-down command and control, and with responsibility for both successes and failures. Retention is not 100 percent, and she thinks it is good for people to take great opportunities elsewhere; Netflix does not expect people to stay forever, only to feel they are doing the best work of their lives while they are there.

She also names two other factors. Leaders need to set a clear vision and strategy and make tough, timely decisions, and she believes people stay or leave partly based on whether the company's direction inspires them. She points to Netflix's newer bets and things being built from scratch for studios, advertisers, and members. Finally, people stay when they are impressed by the talent around them, which she sees as talent density reinforcing itself.

AI tools: pragmatic experimentation

On AI tools for engineers, Stone calls the topic a huge focus, approached "with a lot of intention and pragmatism." The goal is to find where the tools produce higher quality and more business impact. Uses that lower quality or are only about cutting costs are "really not interesting to us."

For coding assistants, Netflix offers teams many tools and lets them explore which ones fit which use cases. Stone acknowledges the learning curve: changing how you write code, document, and make decisions can be jarring, especially for very accomplished people. With tight timelines and big ambitions, there is little free time for this, so Netflix sets aside some weeks where people can focus on trying a new project or experimenting. It collects extensive feedback, much of it self-reported, on which tools help and which should be "graduated" to paved paths. "GenAI champions" across the business help teams troubleshoot, explain what is available, and report back to central teams.

Stone says Netflix does not treat generative AI as a silver bullet and prefers to be "surgical" about where it creates impact. This mirrors the company's approach for member-facing and creator-facing uses, and it shapes infrastructure strategy: giving access to many options, watching where the market solves problems well, and deciding what to build in-house. For internal tech productivity, she thinks the market is likely solving the problems well and Netflix gains little from building its own tools, but the company still wants to be selective about which ones it uses.

Where AI is showing the most promise

Asked whether certain areas are benefiting most, Stone lists several. Prototyping is much faster. She hopes cross-functional teams of engineers, data scientists, product managers, and designers can quickly turn an idea into a visualization or rough code to discuss it. That code is not necessarily production-ready or meant to become a product, and she says that is fine because it helps teams move ideas forward quickly.

She also points to tedious work that is not the coding itself, such as finding out how systems work, documenting code, and automating much of the big migrations Netflix has planned. The third area is detecting and responding to issues: anomaly detection, response, and deep investigations of problems, where she sees a lot of promise for resilience and engineering health. If AI can take over prototyping, documentation, migrations, and detection and response, she argues, engineers have more time for innovative work on architectures, systems, and products that drive business impact.

She repeats that it is not a silver bullet in any of these areas. She adds that the tools have improved greatly since Netflix first tried them a couple of years ago, when, as she puts it, "they didn't meet the quality bar that we really need."

New grads and senior talent

The host notes that Netflix began hiring early-career engineers a few years ago, while many companies now say they will hire only senior engineers until AI's impact is clearer. Stone says the experience with new grads, early-career engineers, and interns has been great. She notes Netflix started from a very different position. At some large tech companies, 30 to 50 percent of engineers were at level three or four, so she understands why a technology shift might lead them to rebalance. Netflix started at 0 percent in most cases, with mostly level five and above.

Early-career hires brought new skills, new perspectives, and energy, and in Stone's view they also bring native familiarity with AI, since recent graduates are used to using it to build products, write code, and solve data problems. She says Netflix will "absolutely" keep investing in early-career talent. At the same time, she is pushing to add more staff, principal, and distinguished engineers and scientists, because many problems need very senior people. Netflix is investing at both ends of the distribution.

She also frames this as developing talent from within. She hopes early-career hires grow into senior technical leaders, and she expects the most senior engineers to be good role models. Netflix now does more internal talent development than it would have five or ten years ago, which she says has been a huge boost.

Open source and encoding innovation

The host says one surprise from researching Netflix was its open source investment. Beyond the well-known Chaos Monkey, a recent report estimated that about one in five Netflix engineers work on open source projects, the highest share among the companies it compared. Stone says perhaps Netflix should talk about this more. She links it to talent density: strong engineers often want to contribute to the wider technical community. Some innovations are Netflix-specific IP kept as a competitive advantage, but many advance the industry in ways that also benefit Netflix.

Her main example is video encoding, where Netflix is heavily involved both internally and externally. She believes Netflix has won nine technical and engineering Emmys for this work and jokes that she used to associate Emmys only with TV and red carpets. The work improves the quality and efficiency of encoding and delivery, which benefits Netflix directly. Netflix is also a founding member of what she calls the Open Media Alliance, an industry group pushing for open advances in encoding technology. When the whole industry improves, Netflix benefits too, including in future integrations. She cites a figure: compared with when Netflix started producing originals, and despite a much larger catalog, she believes Netflix now needs about 60 percent less bandwidth for the same or better quality, which she credits to its encoding innovation. In her view, Netflix "doesn't lose anything, only gains something" by contributing. She also supports publishing more about its work, such as tech blog posts on what it took to build Live.

Advice for new engineers at Netflix

Asked how a new engineer can succeed at Netflix, Stone answers: "Curiosity. Curiosity. Curiosity." It is the value that resonates most with her. She means asking questions and challenging whether the team is solving the right problem in the right way. Being new or early in your career does not mean you cannot be a source of innovation, since great ideas come from everywhere. She encourages new engineers to be open-minded, experiment, take smart risks, and quiet the fearful inner voice that resists trying something new.

Her second piece of advice is to lean on other people. She says Netflix's engineers are happy to help others succeed, so newcomers should find mentors and ask why something works the way it does, what its history is, and which business problem it solves and why. She calls this another form of curiosity, but one that also draws on the wider community at Netflix.

In closing, the host says two points stood out most: how much open source Netflix contributes, with about one in five engineers involved, and how lightweight and continuous its performance management tries to be. Both, the host notes, feel quite different from how most other big tech companies operate.