Building WhatsApp with 30 Engineers: Jean Lee on Saying No, Skipping Process, and Life After the $19B Acquisition
The Pragmatic Engineer
Jean Lee joined WhatsApp in 2012 as engineer number 19, when the app was barely known in the United States. She stayed through its growth to 450 million monthly users, its $19 billion acquisition by Facebook in 2014, and years afterward as an engineering manager at Facebook, including helping start WhatsApp's London office. In this Pragmatic Engineer conversation, she describes how a team of fewer than 30 engineers ran a product that size with almost no formal process. She also talks about what the acquisition looked like from the inside, how performance calibration works for managers at a large company, and whether AI is the real reason today's teams are getting smaller. Her recurring answer is that WhatsApp's small size, trust, and ruthless prioritization mattered more than any tool or methodology.
From a Brewing Scientist's Daughter to IBM
Lee describes herself as a small-town girl. Her father decided to get a PhD in brewing, and the family moved to San Francisco in 1999. That move was her first real exposure to tech careers. She had tinkered with code as a teenager and loved that a few lines could "do things for you over and over." What pushed her toward engineering, though, was talking to adults about their jobs. She considered design and architecture, but the people in those fields discouraged her. In her experience, the people working in tech were the only ones who were genuinely excited and hopeful about their work.
She studied computer science at USC. Her first real coding internship was at a three-person startup founded by a recent USC graduate. The company built a site that aggregated videos from the dozens of YouTube-like platforms that existed before YouTube became dominant, so users didn't have to search twelve different sites. She notes the parallel to today's AI platforms that let users switch between models. At that startup she coordinated with engineers in China, wrote design docs and feature lists, and saw the effect of her code on the live site right away. She loved the ownership and the speed. She also felt that a team made up entirely of new grads was "shooting things to see what sticks," and she wanted mentorship.
That led her to IBM, which she describes as at the time literally the biggest company in the US. She worked there from 2007 to 2009 and valued the veterans who were 20 or 30 years ahead of her and willing to teach. She missed the small-team environment, though. There were many meetings and a lot of process, and she couldn't see how her work contributed to the company. She left in 2009, in the middle of the downturn, which she now considers brave. Her reasoning at 22 or 23 was that she could afford a year off and still catch up. She took classes, did what would now be called gig work, and worked out what she wanted next: a startup again, but a more stable one staffed by experienced people, so she could have both autonomy and mentorship.
Getting Hired at WhatsApp
By 2012, WhatsApp had been around since 2009 and had many users, but mostly in Europe and India. Lee had used it while living in New York, which she describes as an international hub where people already used it. She found the job posting on LinkedIn.
The interview involved no LeetCode-style questions. According to Lee, those only came much later, once WhatsApp started hiring interns and new grads. The conversations were closer to system design: how would you design this, tell me about something you built. She remembers talking with co-founder Jan Koum about messaging apps. Being Korean, she explained a lot about KakaoTalk and how it worked.
The host points out that WhatsApp's Glassdoor page at the time had a single one-star review. Lee doesn't remember checking it. What decided things was speed. She had a verbal offer from another, non-startup company that kept delaying the written offer. Meanwhile, Koum called her a few days after the interview, asked her to come into the office that day or the next, and asked, "What would it take for you to take the offer right now?" She named a few modest things, signed the following day, and got the call from the other company on her first day at WhatsApp.
An Unusually Experienced Team
Lee corrects one assumption. She was not the youngest person there, but about four people were under 30: two new grads, herself, and one other person in their late twenties. The other 15 or so were over 30. The host connects this to investor data suggesting older founders do better, and notes that Koum and Brian Acton started WhatsApp in their mid-thirties after more than a decade at Yahoo and elsewhere.
Lee says many of the first ten or so engineers came from Yahoo. Others came through several channels. Koum personally looked up experts in a given field and contacted them directly. Some came from Acton's Stanford connections, and some were referrals from Sequoia, WhatsApp's investor. The company also relied heavily on contractors in Europe, all very experienced and essentially self-managing. The host adds that about six months before Lee joined, they received an email from Koum titled "career opportunity," after building a Windows Phone app called Cocktail Flow with their brother. They declined, and they now advise listeners to at least talk to a founder who reaches out.
Eight Native Clients and an Erlang Backend
Lee had to look it up to count them all, but WhatsApp maintained eight separate client platforms: iPhone, Android, BlackBerry, Windows Phone, Nokia S40, Nokia S60, KaiOS for a short while, and the web client. Each used its own language and toolchain. The backend was written in Erlang.
Asked why a startup would choose Erlang, a language the host associates mainly with telecoms like Ericsson, Lee points to a talk by WhatsApp engineer Rick Reed at the Erlang Factory conference. She recalls he described running WhatsApp as maintaining an airplane's engine while it flies 24/7. Because the app is so international, it's always 8 a.m. somewhere, so there is never a quiet moment for a break. Erlang was robust and handled concurrency well. According to Lee, the team came across it because they were using another tool that happened to be built on Erlang, and decided it was the right language. The biggest recurring test was New Year's, when everyone sends "Happy New Year" at once. The team would celebrate simply not going down.
The host asks why WhatsApp ignored the conventional advice to use a cross-platform framework or build its own abstraction layer instead of hiring hard-to-find Symbian and BlackBerry specialists. Lee answers with Koum's refrain: he wanted a grandma in a remote countryside to be able to use the app. That grandma probably doesn't have the newest phone with the most memory. So the app had to be lightweight, work on any device, and stay simple. Those priorities, she says, are what drove the decision to build every client natively.
No Code Reviews, No Stand-ups, Just Trust and Dogfooding
Lee calls Meta scrappy compared with other big tech companies, with less emphasis on writing documents. She calls WhatsApp "the ultimate lean company." At the time of the acquisition, fewer than 30 engineers were serving 450 million monthly active users.
There were no code reviews. The one exception was her first commit, when Acton asked to look at it and questioned her about it at length, something like a coding interview. After that, nobody formally reviewed her code again. With only about 30 engineers, people did read each other's Git commits and discussed them in WhatsApp groups. Engineers merged and pushed to production without a manager's sign-off and were trusted to ask when unsure.
The host asks about canarying, feature flags, and experiments. Lee says WhatsApp did little of that. The safety net was dogfooding: before each release, everyone used the build internally. Koum's title at the time was "chief QA officer," which the host had assumed was a joke when they got his email. Lee says it was accurate. He went around trying to break the app, and when he found a bug, he pushed it as far as he could before bringing it to the team.
"No" 99% of the Time
Lee recalls that Koum said no to feature requests about 99% of the time. As a young engineer, she found this confusing. Competitors, especially WeChat, seemed to have every feature imaginable. When she joined, WhatsApp had no groups (they launched shortly afterward), no voice or video calls, and nothing like stories. "All the cool features were missing in my mind," she says, "but that was by design." The priority was that grandma in a remote town being able to use the app reliably at any time.
This connects to what she sees as the main reason WhatsApp won. She acknowledges network effects and being first to market, but says there was plenty of competition, and many rivals were chasing the newest features. WhatsApp was intentional. She says the team was working on video calling around the time the host joined Skype, but didn't launch it until much later, once they were fully confident in the quality. The host notes this is the opposite of the usual startup advice to ship early and iterate. Lee adds that features weren't sitting idle. Employees used voice and video calling internally for a long time, enabling it for a beta list of their own family members' phone numbers before any public release.
The Skype Contrast
The host joined Skype in 2013, around the same time Lee was at WhatsApp. Skype sent everyone to Scrum training, and the host was a Scrum Master. Skype had about 1,000 engineers. Asked whether WhatsApp used Scrum, capital-A Agile, or TDD, Lee says it used none of them. She is surprised that people at Skype felt those practices made them ship faster.
The host defends the process somewhat. With more than 100 teams, Scrum and the structure around it produced a prioritized list of which teams mattered most and should get support. At that size, the host argues, you need this kind of coordination. The lesson they draw is that large organizations move slowly and a small team can outcompete them. Lee adds that at that scale, simply communicating with everyone takes a long time.
Days Since the Last Outage
WhatsApp paid little attention to media coverage or competitors' numbers, partly because hardly anyone was writing about it. The one metric displayed in the office was a counter: the number of days since the last outage. The number was supposed to keep going up, and Lee thinks having it visible may have helped.
On how outages were handled, Lee is careful. The discussions took place in the server team's group chats, which she wasn't part of, so she can't say exactly how they went. She is sure there was no documentation. Blame wasn't a real concern either, she says, because everyone knew exactly who was working on what.
Inside the Acquisition Announcement
Lee journaled after the acquisition and reread those entries for the interview. She was coding with noise-canceling headphones and a Spotify playlist called "let me think." In the small office she could see people bustling around, which was unusual, but she tried to tune it out. Then Neeraj, the head of business and a tall man, started waving his arms to get everyone into the office's single meeting room. WhatsApp almost never had meetings, and had never had an unscheduled one.
Inside, they were told to turn off their phones. Lee wondered whether the company had gone out of business or was raising another round. She didn't think it could be a sale, because Koum used to say selling your company is like selling your baby. They waited a while for one missing colleague, who it turned out was getting her eyebrows done and arrived after the announcement. The founders wanted staff to hear the news before it went public. Lee noticed Koum and Acton making an odd face, which she later recognized as them trying to hide their excitement. Then they announced that Facebook had acquired WhatsApp for $19 billion.
She zoned out for a moment. It was her first startup, she hadn't negotiated her equity, and she couldn't remember how many shares she had. She tried and failed to work out 1% of $19 billion, then concluded that whatever the math, "I'm going to be rich." Mark Zuckerberg then walked in and held a Q&A. The mood mixed excitement and nerves. Several experienced engineers had seen Yahoo change acquired companies completely and lose their essence, and they asked about that. Lee found Zuckerberg charismatic in person and thought his answers were good. He assured them nothing would change and he would preserve WhatsApp as much as possible, "at least that was the messaging at the time."
Handling Sudden Wealth, and Slow Integration
Lee says the company offered a lot of support on the financial side. The business team arranged meetings with accountants and a financial advisor, and invited a professor who had founded Wealthfront to give an hour of advice and book recommendations. Lee read A Random Walk Down Wall Street, which she still recommends, along with several other books, to learn how to manage wealth she had come into at 29.
Day to day, she says, change came slowly. WhatsApp moved to a slightly bigger office but stayed out of Facebook's Menlo Park headquarters for at least a couple of years. Koum and Acton still ran things, and hiring kept its slow, steady pace. Cultural merging started once they moved onto the Facebook campus and began using Facebook's HR and recruiting services. Even then, WhatsApp had its own area and brought its own chairs, walls, and decorations, though mixing increased over time.
The $1 Subscription as a Brake on Growth
Lee says WhatsApp stayed small by choice, not for lack of work. Koum and Acton didn't want to raise much money, and serving users was expensive. Once a year the founders held an all-hands, and Acton walked through earnings and expenses openly. Spending fell into three roughly equal parts: servers, salaries (mostly engineers), and SMS fees for registration codes, which cost around 10 cents each for international messages and added up across millions of users.
WhatsApp was free for the first year and then charged $1 a year. Lee says the fee applied only in certain countries and was used specifically to suppress growth, because growing too fast was costly. After the acquisition, Facebook said it didn't need the dollar, and growth sped up. The less-known part, according to Lee, is that the $1 was enough to cover servers, salaries, and SMS costs, so the company was roughly break-even. It never touched its Sequoia funding, which she recalls as about $8 million. Acton explained that his father had been a business owner who woke up at night worrying about making payroll, and he treated the Sequoia money as a backup.
Starting Over as L3, and Opening London
Facebook engineers all hold the title of software engineer but are assigned levels. As one of WhatsApp's youngest people, Lee was leveled L3, a junior engineer. She wasn't happy about it, but the alternative was giving up her unvested shares. She was promoted several times within WhatsApp and eventually became an engineering manager.
The London office came at Facebook headquarters' request. Menlo Park was running out of space, WhatsApp was huge in Europe, and hiring would be easier where everyone used the product. Lee and two other engineering managers, who had become managers around the same time and trained together, were asked to go. She thinks they were the only ones who could, because others had children and school to consider. One director she worked with couldn't go because his wife didn't want to move the family.
Facebook already had a London office, so the logistics were handled. WhatsApp got its own section. The starting team was two engineers, both converted from contractors (one in England and one in Scotland who commuted in periodically), plus the three managers. Setting up hiring took longer. They worked closely with Facebook's local recruiting team and hired from across Europe and heavily from India. Hiring was much easier than in the US. Lee remembers recruiting at Stanford before the acquisition, when students wouldn't hand over a résumé until she explained what WhatsApp was. In Europe, people were excited to talk to them. The eight-hour time difference was eased by relationships the managers had already built in Menlo Park and by quarterly travel in both directions.
Becoming a Manager Without Asking
Lee never asked to be a manager. Someone on her team begged her manager to let them report to her. She was already the tech lead managing the project, so the move felt natural.
She prepared by reading. Few courses existed then, and in the host's view most good management books appeared after 2015 or 2016, so she read widely on communication and psychology. She particularly recommends Surrounded by Idiots, which covers the DISC personality types. She also thought back on good and bad managers she'd had, citing the saying that people leave managers, not companies.
Her approach was to understand each person individually. One report loved digging into problems and debugging. Another loved building new features and would "go nuts" if handed ten bugs, and that same person was not good at mentoring newer colleagues. She tried to play to each person's strengths while still giving them challenges, and spent a lot of time asking what excited them, what they were good at, and how they wanted to grow.
Calibration: The Manager as Lawyer
Lee is candid about calibration meetings. The biggest misconception, she says, is that your manager gives you a promotion or a raise. A middle manager has no budget and no authority to promote. Directors may have some discretionary budget for rewards, but not even they can grant promotions. At Meta, bonus percentages for each level are set by the compensation team and tied to performance ratings. Lee describes her role as "the lawyer representing my clients": she made the case for her people, but the other managers had to agree.
Asked whether outcomes came down to politics or merit, she points to visibility. Companies have different channels for self-promotion. Some use mass emails, WhatsApp used WhatsApp groups, and Facebook used Workplace, its internal Facebook-style groups and feed. She noticed that engineers who posted most often reached consensus most easily. If she knew nothing about someone and their manager said they were great, she had no basis to agree. If that person had been posting about their work, its impact, what they learned, and who they worked with, she already knew them, and could even ask questions in the comments and see how well they had thought things through. The host summarizes that success at Facebook partly required being good at using the Facebook product internally.
Asked what the best engineers shared, Lee pushes back on the premise. "Good engineer" might mean someone who ships features quickly, someone who designs complex systems, or someone who can explain it all to non-technical people, and the definition varies by company. At Facebook, she agrees, it came down to impact, and impact was largely measured through those posts.
Burnout, Six Months of Nothing, and 100 Founder Conversations
The London office stopped feeling like a startup after about a year and a half, when Lee realized she didn't know a colleague's name. At WhatsApp she had known every engineer, where they lived, and the names of their spouses, children, and dogs, and she says that group still keeps a strong bond. Her London assignment was a two-year contract. When it ended she could stay in London or return to Menlo Park, but after eight years, and with a personality that wants "an A+ on everything," she was burned out.
Knowing she doesn't take breaks, she set herself a goal of doing nothing for six months. She read, exercised, took long walks, and went on several meditation retreats. Later in the conversation she says the break actually lasted a year and that she read 100 books during it. Afterward she talked to 100 founders, tracked in a spreadsheet, looking for a company to join or start, and found she wasn't passionate about any of them. She realized the part of WhatsApp she had enjoyed most was managing: creating a supportive culture where people could learn and thrive without someone "breathing down your neck," and unblocking whatever each person needed. Since that didn't require starting a company, she moved into mentoring, coaching (which she no longer does), writing, and YouTube.
She had just passed 100,000 YouTube subscribers but nearly quit early on. Her grandmother escaped North Korea during the war, and Lee says that culture taught people not to speak or be seen in public because it was dangerous. She thinks generations of that fear stayed with her. When one of her early videos went viral, she felt so uncomfortable she almost stopped, until a mentor told her it was fine to do something she enjoyed and to give it a shot.
Is AI Really Why Teams Are Smaller?
Lee is skeptical of the idea that AI explains today's smaller teams. She wonders whether small teams are efficient simply because they are small. WhatsApp had no AI and was efficient anyway. She struggles to name a current team as small as WhatsApp's with comparable impact, suggesting Anthropic might come to mind but that even it is larger. She sees a shift in mindset. People used to brag at networking events about hiring a thousand engineers, and investors treated headcount growth as a sign of health. Now investors think smaller is better. Her hypothesis is that companies hiring less have found new efficiency as a byproduct and credited it to AI.
She uses AI tools daily as a thought partner, for example asking ChatGPT to act as an executive coach or "a Harvard-trained futurist" to spot trends. She thinks engineering management is less exposed, because it depends on person-to-person work like asking questions and getting to know engineers. The parts of the job built around OKRs, process, and documentation will shrink, and she's glad about that because she doesn't think they were necessary. Performance management is one example. She used to painstakingly gather everything her engineers had done before calibration, which gave her an advantage over managers who didn't. That was unfair to engineers on other teams, and she thinks agents that gather this information could remove the advantage. She also recalls that WhatsApp once had an engineer whose job was essentially adding code comments, something she says AI now does well.
Lessons for New Grads and AI-Native Startups
Her advice to new graduates is to focus on foundations: tools and languages come and go, foundations don't. For AI startups, she draws on the cycles she has lived through. There were dozens of video-sharing sites during her internship and dozens of messaging apps during her WhatsApp years, and both markets eventually consolidated. She believes AI is in a similar phase, with so many tools that decision paralysis is easy. Her remedy is clear goals: know what you're building and why, or what you're learning and why. Otherwise you "might work really hard and end up nowhere."
She agrees with the host's summary that WhatsApp succeeded by doing its core thing well and adding features slowly while competitors got distracted. She also offers it as a way to evaluate founders. Imagine a founder who is the opposite of Koum and says yes to every idea. As a twenty-something engineer that might feel great, but the company would end up all over the place.
The practice she most wants modern teams to borrow is leanness, which she says brings ownership and freedom. Koum and Acton were specific about what to build, but how to build it was open for debate, and they drew answers out with questions: what is the problem, what are the different approaches? Her first code review with Acton made her think critically. Because he never reviewed her code again, she knew she was responsible. "When you give responsibilities to people, people will step up," she says, adding that not everyone does, but most people will.
The host asks whether the industry has been "over-babying" new grads by assigning mentors for six months to a year. Lee answers with a metaphor. Hiring smart people is like a mold, and if the mold is too small, that becomes the limit of how far they grow, and you throw away material that could have been excellent.
Books, and the Host's Takeaways
Lee's recommendations are What Color Is Your Parachute? for understanding your strengths and priorities, Surrounded by Idiots for communicating with different personalities, and A Random Walk Down Wall Street for managing money. For fiction she picks The Hunger Games series, for its story of a woman overcoming her challenges.
In closing, the host highlights three points. First, most processes exist for audits, accountability, and tracking who did what, which are problems created by scale rather than by the work itself. With 30 people who can see each other's work, you can just talk. Second, the Skype comparison shows that organizational discipline and actual shipping speed are not the same thing. Third, Lee's "lawyer" description of calibration shows that the engineers promoted most easily were not necessarily the best, but the ones who made their work visible to managers who had never worked with them. The host calls this an uncomfortable truth that every engineer at a big company needs to hear.
I have a feeling WhatsApp was not exactly a standard startup.
So, we didn't have code reviews. But, the only time I got my code reviewed was the first time I made a comment.
And you said that Jan said no a lot.
99% of the time he was saying no. All the cool features were missing in my mind, but that was by design because we really wanted to prioritize again the quality of a grandma in a remote town being able to use our app at any given time.
Scrum, Agile with a capital A, TDD. Did you use any of these at WhatsApp?
I'm surprised to hear they thought they were shipping faster because of it. We didn't use any of it.
So, you were break even. Yeah, that $1 was enough to pay for the server cost, the salaries, and the SMS cost every year.
Jean Lee was engineer number 19 at WhatsApp. She joined when hardly anyone in the US had heard of it, saw it grow to 450 million users, and was sitting at her desk with noise-canceling headphones on when news broke that Facebook bought them for 19 billion dollars. In today's conversation, we discuss how WhatsApp built natively eight different platforms with a team of 30 engineers. Why the founder said no to almost every feature request for years. How WhatsApp's team operated with no code reviews, no stand-ups, no sprint planning, and many more. If you want to understand how a tiny team with almost no process built one of the most successful products in history, and what today's AI-native startups can still learn from them, this episode is for you.
This episode is presented by Statsig, the unified platform for flags, analytics, experiments, and more. Check out the show notes to learn more about them and our other season sponsors, Sonar and WorkOS.
Jean, welcome to the podcast. It is amazing to meet you. You have quite the story, early engineer at WhatsApp. But, before we get into WhatsApp, how did you get into tech?
I've always been a small-town girl. My dad was an OG hipster. He was really into brewing beer. So, he decided to get a PhD in beer.
In beer? Yeah. In brewing. In brewing.
So, I moved to San Francisco in 1999, and that's when I got really exposed to all the different tech roles, like growing up, I didn't really even think about engineering as a job. Of course, I used computers, and I thought it was really cool to be able to use Yahoo and search things online, but beyond that, my first exposure to Silicon Valley and tech came from living here. I got to meet a lot of people who work in tech. I dabbled around with coding when I was a teenager, but not too seriously. But, I did think it was really cool that you can just write a few lines, and they will just do things for you over and over and over. It was almost magical.
I loved the feeling of creating something that actually runs, and debugging something and fixing it, and it runs again. That was really joyous, and I didn't really get into like super into coding until I went to college, but one of the reasons why I decided I wanted to go into coding was I talked to different people. So, I thought maybe I want to be a designer, maybe I want to be an architect, maybe I want to be an engineer. And I talked to different adults who work in the industry.
After talking to a lot of adults, I realized people who are in tech were the only ones who were really excited about their jobs. So, in Silicon Valley, when you ask people, like tell me about your work, people are often very hopeful for the future and very proud of what they're building. Compared to when you ask adults that I spoke with, they were not so encouraging. They're like, "Oh, don't become an architect. Don't become a designer." So, that was one of the influences for me early on.
I studied computer science at USC, and one of my first internships, actual like coding internships, was at a small company. It was a three-person startup started by one of the new grads from USC. And you'll probably understand it was a video sharing website.
But, it was not like YouTube, but there were so many versions of YouTube back in the days before YouTube was dominant, right? So, you probably remember dozens of these video sharing platforms.
And one of the issues of having so many options is that you have to be visiting 12 different sites to search for any things. So, we had a website where you can aggregate all the different types of videos from different sources. Which is actually kind of funny because lately I've been seeing a lot of AI platforms where you can just switch between the models. Very similar to that.
Yeah. How did you get into IBM?
I really loved working for a small three-person startup because I got to work with engineers. We had engineers overseas in China. So, I got to work with them. I got to also do a little bit of coding myself, but I was coming up with the design docs like the features list and I was calling a lot of the shots and I could also directly see the impact of my code immediately on the website. And I thought that type of ownership and speed and the visibility was really exciting that I get to see the impact of my work immediately.
But, one thing I wish I had was a little bit more mentorship because we were all new grads and in college I felt like we were just shooting things to see what sticks. And I thought maybe for my first job out of school, I would like a little bit more mentorship and training and I started looking at more bigger companies, more traditional companies and that's how I ended up at... At the time it was literally the biggest company in the US.
At what point did you decide that you wanted to leave or try out something else? Or did you even decide or something just came up?
One of the reasons why I wanted to go to a more traditional company with more structure was so that I could get more mentorship and training and IBM was excellent for that. There were so many veterans, they had so much experience, and they were willing to share with me because they were 20, 30 years ahead of me, right? But, one thing I really missed was the small team environment. It was just so big. There was a lot of meetings, a lot of process, and I missed seeing the impact of my work. I couldn't quite understand how my work was contributing to the overall company. So, then I decided to take some time off and explore and have some fun.
Yeah, and on what time was this? What year was this?
So, I started working in 2007, and I left by 2009, which was actually in retrospect, I was really brave because it was in the midst of economic downturn. My thought process at the time was I was only 22 or three, and I figured even if I take a year off, I can still catch up, which I did.
And what happened from there? How did you eventually get to WhatsApp? That was years later, right?
Yeah, so I took some time off to try out different like classes. I took a lot of classes. I did a little bit of... Nowadays you call it the gig work, but I did all kinds of work. So, whatever I needed to, you know, make a living while taking all these classes and exploring and really finding out what like what kind of environment or what kind of career do I envision for myself. And after I took those time off, I decided that I want to go back to Silicon Valley, but this time I do for a startup, but maybe with people who are a little bit more experienced, maybe not new grads, and maybe not a three-person startup, but a little bit more stable startup where I can possibly get both the autonomy and the impact of the work, but also a little bit more mentoring because I was still in my 20s.
Okay, so how did you find this startup, which of course happened to be WhatsApp?
In 2012, WhatsApp was still early. They started in 2009 and they did still have a lot of users, but they're mostly in Europe and in India. They were not very known in America.
Were you a WhatsApp user back then?
I was not, but my wife and her friends were or back then my girlfriend, but so some of my friends were using it on and off. It was kind of starting to be big in Europe. It wasn't as massive just yet.
Exactly. I was lucky because I actually lived in New York for a little bit before moving here and a lot of people in New York were using it because it's an international hub. So I had used a product in the past and I saw the job posting on LinkedIn.
And then you applied? What was the interview like?
I don't think we did any LeetCode until way way later until when we started hiring interns and new grads. Most of the interviews were talking about... I guess you can call it system design interviews. We would talk about how would you design this? How would you design that? Like tell me about your past experience building this product. And I recall talking to Jan about different messaging apps. And being Korean, I told him a lot about KakaoTalk and how it worked. Yeah, that was my interview.
Just like that you got an offer. I guess it's a startup, right? Things move fast. Like but I assume it must have been quick turnaround offer and then you have to decide, right? How did you decide that you're going to join this relatively unknown startup that is building some cool messaging that you kind of thought was cool, but there wasn't much information about that. In fact, their Glassdoor rating at the time I remember had a one star. It had one review, one star someone saying, "Oh, I don't like working here." Who knows if that was even a real employee, but that was their Glassdoor.
Oh, that's so interesting. I don't remember looking up... I must have looked up Glassdoor, but like I was really lucky because I actually had another offer from a different company, but they were a little bit slow.
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It was not a startup, and they said, "Oh, hey, like you have my verbal offer. I am going to give you a written offer soon." But then it took them a while, and meanwhile Jan called me a few days later after the interview, and he said, "Come into the office right like today or tomorrow." Yeah. And then he asked me, "What would it take for you to take the offer right now?"
Love it. What did you say?
I mean, I wasn't looking for that much. I mean, I was in my 20s, so I just told them, "Oh, like a few things I would like to have, then sure, I'll take the offer," and I saw and signed the offer the following day. And I did actually hear back from the other company on the first day I started WhatsApp. They called me, and I was like, "Oh, I just started a new company."
Hey, that's it with startups: if you move faster, or otherwise don't be surprised. So, you were engineer or you were employee number 19 at WhatsApp, right?
Was engineer number 19.
Engineer number 19 at WhatsApp. And you told me something really interesting that you were the youngest person even though you were like by this time at your mid 20s or so.
I thought about that. So, I recall there were about four of us under the age of 30. So, I was not the youngest, but there were two people who were new grads. And then myself and one other person who were in our late 20s. But the other like 15 or so people above 30 at the start.
Which is kind of unheard. Why do you think this was? This is so interesting.
That is true. Is it still rare nowadays? Like...
Good question. I think these days it might not be as rare, by the way. I think so because I think I read some kind of statistics from investors that actually when they look at the success rates of startups, they found that older founders tend to do better.
Yeah. And then WhatsApp, I guess you know, like Jan and Brian, they started this at like mid-30s or so after they spent like more than a decade working at Yahoo and other places.
Exactly.
Yep. So, I guess they must have been able to hire like their network whatnot.
Yeah, the first 10 or so engineers, a lot of them came from Yahoo. Some came from Europe. You mentioned the story when Jan reached out to you. Jan used to do that. He would just look up who is the expert in this field and reach out to people and we had a lot of contractors in Europe. And then we had some like mostly from personal connection like from Stanford because Brian went to Stanford. And then we had some referrals from Sequoia because they invested in WhatsApp.
It is just fascinating because the way we connected actually is both of us know Jan. I mean, you've worked with him, but I had an email in my inbox from him, I think 6 months before you joined WhatsApp where I got a message from him and saying... I built a Windows Phone app at the time together with my brother called Cocktail Flow. And it was a beautiful Windows Phone app and it was labeled career opportunity. So, what you're saying is there's a alternative timeline where if I said like yes, I'm interested, which in hindsight if a founder reaches out, you probably should at least talk to them. Don't make the mistake that I did which is just saying like I'm sorry, I'm busy. I might have been a contractor from Europe. So, like this sounds like that was a strategy and that was a smart strategy.
Yeah, we had many contractors in Europe and they were all very experienced people. They were basically managing themselves. We had people all over the world working with us.
What was the tech stack like at WhatsApp?
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We were actually pretty unique. I don't think any startup ever really does this, but we had seven different stacks. We had... I actually looked it up because it's hard to count them all. We had of course everybody has iPhone and Android, but we also had BlackBerry and Windows Phone, which is also pretty common, but we also had Nokia S40, S60. We had a thing called
KaiOS for a while, but not for a long time, and we had the web client. So, it's actually eight. So you have, of course, you know, we know that iOS is Objective-C, Android was Java back in the day, and then all of these, like the BlackBerry, the Nokia, they all had, I think Nokia was Symbian C++. They all had like their own different language. And then we've not talked about the back end, right?
Mhm, and the back end was Erlang.
Erlang. Can you tell us about Erlang? Because that is one of the most exotic tech stacks. I've heard Erlang in telecommunications context at Ericsson, again in Europe. It is popular with the telcos, but startup-wise, I'm not sure I heard anyone else use Erlang.
You might be right. They do have an Erlang conference. I think it's called Erlang Factory. There's a really great talk by one of our engineers, Rick Reed, if you're interested in learning more about it, but
Or we'll put it in the show notes below.
Yeah, I'm pretty sure that it's still on YouTube. I haven't looked at it recently, but he gave a really great talk about why they started working with Erlang and then it was the perfect choice, and he describes it as trying to maintain the engine of an airplane while it's flying 24/7.
Because if you imagine, like, WhatsApp is so international, we can't take a break, right? We have to continuously keep running, and it's always busy. If someone's, it's 8:00 a.m. somewhere in the world, right? And Erlang was a really robust language that was really good at concurrencies. And they stumbled upon it because they were using this other tool that happened to use Erlang and decided this is the perfect language.
And I guess at the core of WhatsApp, what was the core engineering challenge? Was it like so many messages kind of coming in needing to be seated out and sent to different, you know, platforms?
Platforms. Yeah, that was one of the main challenges. Like, for example, for New Year's or Christmas. Because everyone's saying "Happy New Year" at the exact same moment, and that was always our biggest challenge every year, and we would celebrate, "Hey, we didn't go down after New Year's."
So the interesting thing about the seven different mobile platforms specifically is the conventional wisdom before and after has been like, look, if you want to support all those platforms, don't be silly. Do cross-platform, either build your own layer that is cross-platform or use, you know, there's all sorts of frameworks. Why did WhatsApp not do this? Do you remember the discussions of like why hire seven, including some really hard to hire people, like for Nokia and Symbian, and you mentioned the contractors in Europe. I mean, it sounds a bit of a nightmare. Why?
And so Jan used to always say, "I want a grandma in a remote countryside to be able to use our app." So what does that mean? They may not have the newest iPhone, the shiniest phone with the biggest memory, right? In the countryside where a grandma is using it, you need the app to be lightweight. You need it to work on any kind of device. And you need the app to be simple. So those were our goals and priorities, and that's the thought process that went into our decision to build seven different platforms.
And then inside WhatsApp, how did you get things done? Do you remember like how a project got done, or what was the concept of projects and kind of what engineering processes people might have followed, especially, you know, later you worked at Meta, compared to like how, you know, more kind of standard startups work? Cuz I have a feeling WhatsApp was not exactly a standard startup, was it?
Not really. Even Meta, compared to other big tech, especially when I was at Meta, was pretty scrappy. Like, not so much on writing documents, for example. So the move fast and break things model kind of allowed them to be a little bit more lean in terms of their process, at least while I was there. But WhatsApp was like the ultimate lean company. By the time we were acquired, we only had 20-something engineers, so under 30 people serving 450 million monthly active users.
So we didn't have code reviews. The only time I got my code reviewed was the first time I made a commit. Brian asked to take a look at it before I committed it, and he asked me a bunch of questions which I had to think through a lot, kind of like a coding interview. But that was it. After the first time, we didn't really have a formal code review, but I mean, people read the Git commits because there's only 30 engineers, so you can read other people's code, and they would discuss it on the WhatsApp groups.
So everyone was trusted, all engineers, that they just pushed their code, they merged it into production, pushed it to production without a manager review, and it was trusted that, you know, they would ask if they were unsure or something like that.
Exactly.
Okay, and it worked. It worked. What about the release process? Like if you tell me 450 million people, the first thing I'm going to say is like, okay, did you do canarying? Did you do feature flagging? Did you do experiments? Did you do, you know, what kind of safety nets did you have, right?
We didn't do much of that, but we were really big on dogfooding. So, every time we were about to do a release, we would all internally use it ourselves. Jan, I think he might still say it on his LinkedIn. If you look up Jan, it said just quality engineer. His title, when he messaged me, cuz I didn't know he was CEO, it said chief QA officer. And I didn't know what that meant. I thought it was some sort of weird joke from the outside. So, now it makes sense. So, he was going around. He was making sure that it worked. He would try to break things as much as he can. And then if he finds a bug, he will really try to break it, and then he'll come and say, "Hey, like, I found this bug."
And you also said that Jan said no a lot.
He did say no. As I recall, 99% of the time he was saying no. Which, again, as a young engineer, I was very confused, because when you look at all these other apps, there were like a dozen different messaging apps at the time. Like WeChat is notorious for having everything, right? They have so many features. And I was so confused, like, why don't we build all these features? These are the newest, coolest things that we should have. Because at the time when I joined, we didn't have groups. We launched groups shortly after I joined. We didn't have voice calls, video calls. We didn't have any of these, no stories, you know, all the cool features were missing in my mind. But that was by design, because we really wanted to prioritize, again, the quality of a grandma in a remote town being able to use our app at any given time.
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With this, let's get back to how Jean and the WhatsApp team shipped quality code with close to zero formal processes.
So, it sounds like WhatsApp had very, very little process. This was very, very interesting, because I worked at Skype at the same time as you joined WhatsApp. I joined Skype in 2013, and you joined WhatsApp in 2012. Skype was very proud that they sent everyone to a Scrum training. I was a Scrum Master, other people were Scrum Masters. So, here we were with all the Scrum, all the consultants, all the everything, and WhatsApp had defeated us with a lot smaller team, and no Scrum, no TDD, no Agile.
At Skype? 1,000 engineers.
Wow. That was a lot of people. Yep. I mean, when you have 1,000 people, you kind of need these.
Yeah, and in all fairness, for example, one thing that this whole Scrum thing solved for a little bit is we had more than 100 teams, and everyone was working on different things, and because of all this organization, we had a prioritized list of which teams are the most important, and those got all the support. So, I guess one lesson might be that when you're just big, it's just so much harder to move fast, and a small team can outcompete you.
Yeah, it just takes a long time even just to communicate with everyone.
Being inside of WhatsApp, how did it feel to see this massive growth, not in your team size, but in the product usage, the, you know, the people, the media, the feedback?
We didn't have much media. Like, nobody knew about WhatsApp.
One interesting thing you told me about the office is you had countdown displays. Can you tell me about them? What were these? What did they display?
Yeah, so you asked me a lot about metrics, and I think really the only metrics we tracked, like, we didn't really pay too much attention to media or Skype's usage numbers or other messaging apps' usage numbers, but the one metric we counted was number of days, like X number of days since the last outage.
Wow. No pressure.
Well, the numbers had to go up over time. Maybe that helped to have it visibly there. And when an outage happened, do you remember what happened after? Because these days in the tech industry it's all about blameless postmortems. If an outage happens, you know, we first mitigate, then we get together, then we write a document where we try really hard to not say who caused this, but we come up with why the system is like this and so on. How did you go about dealing with outages and also following up and ensuring that they won't happen again?
Today I know they did these discussions in the server group chats, but I wasn't in the server group chats, so I can't really say for sure. I mean, for sure we did not have documentation.
It sounds like a lot of things were pretty simple. You talk with people, if you have a problem, you try to fix it. Don't over-document things for no reason, and it seemed to just work. And then have the key thing, like, I guess if you put out days since outage, people will know like, okay, I should do what I can to not have an outage.
And everybody knew exactly who was working on what, so we didn't have to blame anyone. Everyone just knew.
WhatsApp was a massive, massive, massive success. What do you think made it so successful in the early years, especially for the product itself? You know, you've seen Kakao, you were aware of some of the competing messaging apps. What did WhatsApp do that others did not?
There is a little bit of the network effect. The thing about a messaging app is that if you use it, you need your friends to use it, and if your friends use it, you need to use it. And WhatsApp was the first to be on the market. That certainly helped, but there was a lot of competition. But again, I think a lot of other apps and messaging apps were chasing features, thinking about adding the shiniest, newest features. Whereas WhatsApp was very intentional. They actually worked on video calling for a very long time. We were probably working on it by the time you joined Skype, when your founder said, "We have video." We were working on it, but we just didn't launch it until much later, when we were actually like 100% sure about the quality of the feature. So, we often held onto features until we felt really sure before launching them.
Interesting, cuz that is a little bit different than the conventional advice, which is if you're a startup, launch early, get feedback, improve it, and iterate on it. Sounds like you did the opposite. It's like polish it and then do it when you have full conviction.
Yeah, we did use it internally. Internally, we used the voice and the video calling features with our families. So, we had like a list: okay, like, I have family members, these are all my parents' and my brother's and sisters' numbers. Let's enable it for this beta group. And we used it for a very long time before we launched it to the public.
Two years into working at WhatsApp, in 2014, Facebook announces their biggest ever acquisition, WhatsApp for 19 billion dollars. What do you remember of this time? How unexpected was it, and what kind of feelings, what kind of emotions went through you and the team around you?
I actually journaled soon after the acquisition, so I looked at my journal around this time, 2014. So, it's been over 10 years. But I looked at my journal, and I remember I was coding. I had this Spotify playlist with noise-canceling headphones. I had this playlist called, let me think. This is the one I listen to when I want to focus. And again, we were in a pretty small office where I can see everything. I was sitting in a pretty central location, so I could see people bustling and hustling, which was a little bit weird, but I tried to tune it out so I can code.
But then, from the side I saw Neeraj, who was the head of business at the time. He was just waving his arms. He's a pretty tall guy, so I could see it. He's like, stop whatever you're working on right now. Come into the, we had one meeting room. Come in. Come into the meeting room. And I was like, what is happening? Like, we never have meetings. Like, we never
So, you didn't have meetings?
I mean, we had scheduled meetings every now and then, but we had never had unscheduled meetings. And we rarely had meetings at all. So, I was confused, and I dropped whatever I was working on and I went into the conference room. And then they asked, like, turn off your phones. WhatsApp, turn off your phone. That's kind of weird, right? And I thought, oh my gosh, what's happening? Like, did we go out of business? That was one thought. I thought, are we getting another round of funding? Like a new investor coming on board. It can't be that we sold the company, because Jan used to say he will never sell the company. He used to actually say selling your company is like selling your baby.
And I remember we were waiting for quite a while because there was one person missing. Oh. And it turns out she was getting her eyebrows done.
With your phone, like, by the way.
Yeah, she came after the announcement, but the news was about to hit the public and they wanted to tell us before the news hit. And I noticed that Jan and Brian were making this face, and I couldn't tell what it was. And then they made the announcement: WhatsApp has been acquired by Facebook for $19 billion. And I realized, oh, that was them trying to hide their excitement. That was the face.
Kind of smiley but not smiley.
And that was a really exciting moment, and I kind of zoned out for a little bit because I was trying to remember, hey, like, how many shares did I get? Again, it was my first startup ever. I didn't even negotiate my equity, and I honestly couldn't remember how much equity I had, and I was trying to think, how much is a billion dollars? It seems like a lot of money. And how much is like 1% of 19 billion? I couldn't do the math. And I remember
Sitting there thinking, like, trying to do the math. And then I thought, you know, no matter how the math works, I think one thing is clear. I'm going to be rich.
And then Zuckerberg walked in. Zuckerberg walked in, sat in a meeting.
Yeah. Wow. And then you had like a Q&A or something?
We did. We did. Yeah. What kind of questions can you ask at this point? Or what kind of questions did people ask? There was a mix of excitement and nervousness, right? Are we going to have to change everything? Because I think a lot of the engineers were more experienced and they talked about how when Yahoo acquired companies, they changed 100% and lost the, what is it, the essence of the business. So there were a lot of questions around that, and
Mark is actually very charismatic in person and I thought he had great answers at the time. He made sure everyone feels assured that nothing's going to change and he will try to maintain it as much as possible. At least that was the messaging at the time.
Clearly this was an amazing exit and to this day it's not really been repeated. Maybe a few companies might have come close, but definitely not with such a small team. How did you and your colleagues deal with the fact that, wow, you've just got an amazing financial exit, but I guess the company kind of continues inside of Meta? It seems like two things at the same time: okay, I have this amazing financial exit, but there's also work. How do you balance? How did you balance? How do you decide what next?
That's twofold. So the finance side, in terms of that aspect, we actually got a lot of support. Our business person organized many meetings with the accountants or even a financial advisor. We invited a professor who was a founder of Wealthfront and he gave us an hour of finance advice and he recommended books. I read A Random Walk Down Wall Street, which is a great book. I recommend that people read it if you're interested in financial management, and I read several other books to really educate myself to be able to manage this new wealth that I came across as a young 29-year-old.
Yeah. What changed in the day-to-day once you officially became part of Facebook? Did you have to move offices? Did you get a new title added to the Meta org chart, that kind of stuff?
The changes were very slow in the beginning. We didn't even move into the Meta, or at the time it was called Facebook, headquarters in Menlo Park until at least a couple years after the acquisition. So, in the beginning, everything was same as usual. We still had our old office. Oh, we did actually move to a little bit nicer office, a slightly bigger office. But other than that, it was business as usual. It was Jan and Brian. And we were hiring, but not, you know, at our similar slow, steady pace. And I think not until when we actually moved into the Facebook office, we started seeing a little bit more cultural influence and merging. Like, we started using their HR services, their recruiting services, and things like that. But it was a very gradual change over time.
And then when WhatsApp became part of Facebook, as I understand it, it still is even to this day its own organization inside of Facebook. I understand there's organizations like Messenger, or there's the Facebook group, etc. So did WhatsApp remain its own kind of organization, a little bit shielded from the rest of Facebook?
We had our own area. Yeah, or your own what? And in the beginning, we even had our own chairs and our own whatever, like walls and decorations that we were using; we brought them all over. But over time, you know, there was more and more mixing.
After the acquisition, how did you start to hire more people? How did the projects change? Did things become more ambitious? Did you start to add more features? Because clearly there were about 30 of you, and then in a few years there were hundreds of people working on WhatsApp; these days it must be thousands of people. And what new work came up for those people? Because again, originally WhatsApp was so minimalist, right? And kind of so scrappy.
I guess we were choosing to be small, not that there was not enough work for us to do, right? So one of the reasons why we also tried to remain small was actually Brian and Jan did not want to raise too much money. And it actually cost a lot of money to serve so many users. You have to pay for the servers. You have to pay for the SMS registration codes. Every year Jan and Brian would do an all-hands meeting. So we did have meetings.
Once a year?
And Brian was very transparent. He would walk through our earnings and expenses.
Ooh, interesting.
Well, I had a lot of information around it. So the three main buckets of our spending: server cost was about a third, and then about a third on salaries, for the engineers mostly. And then a third, the rest, was for the SMS fee. When you try to register you get that code, and we have to pay that 10 cents or however much it cost to send that international messaging. Those numbers add up when you have millions of people using your app. So they actually didn't want to grow too fast because it gets very expensive. WhatsApp was free for the first year and then after that WhatsApp was charging $1 for every year. But they were only using it in certain countries, really to suppress growth, because they didn't want to grow too fast.
Fascinating. Because I remember in Europe and in the US there was this $1 cost, which I think people were like, yeah, well, whatever. I don't think we realized that this was a growth suppression tactic. Fascinating. And then when Facebook acquired, I guess they got rid of it.
Yeah, Facebook said we don't need the dollar. We can grow as much as we can, because they had the funding for it.
Growth just... did it speed up? Do you remember? It did, yeah.
Incredible detail. You're using payment to slow down growth.
A lesser known detail about the $1 is that that $1 was enough to pay for all of these: the server cost, the salaries, and the SMS code. Per year.
So, you were roughly break even?
Break even. We did have funding from Sequoia, but we never touched that money.
Incredible. Yeah, Brian explained it as how his dad was a business owner and they would wake up in the middle of the night worried, "What if I cannot pay the salaries for the employees tomorrow?" And he explained that he took the funding from Sequoia as a backup. And I think it was $8 million of funding, if I recall, if I looked at the backup. Yeah, so we never touched that money. The $1 paid for everything.
And it slowed down growth enough to be manageable. Yeah.
When you joined Facebook, what title did you get and how did your career change?
So, the thing about Facebook is that everyone's actually a software engineer. I'm pretty sure they still don't have titles.
They don't have titles, but they have levels. What level did you come in at?
So, being one of the five youngest people, I got leveled as a junior engineer.
No, you did not.
L3 or L4? L3, L3, yeah.
No.
To climb all over again. Oh my gosh, that must have been a bit awkward.
I was not too happy about it, but what's the alternative? Do I want to give up vesting the rest of the shares? And eventually I got promoted.
But that was within WhatsApp, so you got promoted pretty quickly. How many times did you get promoted there?
A few times. I mean, I eventually became an engineering manager.
And then, as you became an engineering manager, at some point you decided to help and start a new office in London. How did that decision come, and how did you go about it?
That was actually an ask from Facebook headquarters. So, they said, "Hey, we're actually running out of space in Menlo Park. And also, WhatsApp is so big in Europe, so why not have a presence there? It'll be much easier to hire engineers because everybody actually uses WhatsApp. So, let's start a new office there." And we didn't have that many engineering managers, right? I was very lucky because I got asked to go along with a couple other engineering managers, and all three of us actually became managers around the same time. We actually even trained together. So, we were relatively new managers when we got asked to go there, but I think we were the only ones who could go because, you know, people have children, and they have to think about school, and they couldn't go. I remember one, the director that I was working with, he couldn't go because his wife says she doesn't want to move with the children.
It makes perfect sense. You arrived in London, you landed with these two or three other engineering managers. How did you start to grow the office? From a practical perspective, what can I imagine? Like, how did you start hiring or leasing space? Or what are the other things that you had to do that were maybe a little bit unexpected for you?
A lot of the logistical part was taken care of for us because Facebook already had an office there, so we kind of moved in. We got our own section. And it wasn't big because at the time, again, we had a lot of contractors in Europe, so we had one contractor already in England. So, we converted them full-time, and then we had one in Scotland. We also converted him full-time, so he would commute from Scotland every now and then. So, we had two engineers plus three managers, and we started hiring there.
I think the hiring part was something that took longer to set up. We worked very closely with the Facebook hiring team, which was really great, that we already had people who were familiar with the local recruiting logistics there. So, one thing we focused on a lot was really letting engineers know, "Hey, WhatsApp is hiring in Europe now. Come apply." Because we were hiring from all over Europe and also a lot from India.
Do you feel it was easier to hire for WhatsApp in Europe just because people knew about it? Did you get more excitement, more applicants?
100%. You wouldn't believe. Like, I used to do a lot of university recruiting, and when I used to go to Stanford, maybe 2013, like anytime before the acquisition, the people would come up to the booth. And I would say, "Hey, do you want to give me your resume?" And they would be like, "Tell me about your company first." Because they have never heard of WhatsApp. What is this company? I'm not even going to give you my resume.
I only have one resume. I have only 20 of these.
Exactly. Versus in Europe, people were actually excited to talk to us.
What were the good and bad things of working in what basically is a remote office? Like, yes, London was a big office, but HQ was in California, Menlo Park. That's 8 hours of time zone difference, a lot less overlap. There's probably some good things about this and some downsides.
It helped because the three of us were from Menlo Park and we actually had great relationships with other teams and other engineers and other managers. And we also traveled back to Menlo Park every quarter, and then we had the leadership from Menlo Park also travel to London almost every quarter. So, there was a lot of back and forth to really strengthen the relationship in the beginning.
Your growth went to being, I guess, one of the most junior people in WhatsApp, which is crazy to say because you were experienced as well, but then you were also L3 in Facebook, which I still cannot believe. But you went and became a manager. What pushed you to actually say, "I actually want to try to manage people"?
I actually never asked for it myself. Someone on my team begged my manager, "Hey, can I please report to Jean?" And that's how I became a manager.
Wow. Okay. What do you think this person saw in you that they wanted to report to you when you were not a manager?
I was the tech lead, so I was already managing the project. So, it was sort of a natural transition for me.
And when you become a manager, what parts of the job came naturally to you and what parts were hard that you had to learn or get mentorship for?
You know, I started reading books. I love reading books. Whenever there's a new challenge, I like to read, learn, and research. There actually at the time weren't a lot of courses on how to become a manager. And not a lot of books.
Like, I still don't think there are too many books about how to become a manager. There's a little bit more now. There's like three or four good ones, but they all came out after like 2015 or 2016.
Yeah, the resources were pretty limited, but I did what I can to read as much as I can about leadership, and I think I read actually a lot about communication and psychology. There's several books; like, I love the book Surrounded by Idiots. Have you read that book? It talks about the DISC personality, the different types of personalities. And I try to really understand what motivates people, how do you communicate with people in a way that makes sense to the other person. And also I reflected personally on what were some good managers and bad managers in my experience, because you hear the saying that people don't leave companies, they leave managers, right? Your manager can really make or break your career. And they can make your life miserable if you're, you know, matched with someone you don't vibe with.
What are the traits that you found, as you recalled? What were things you said, like, I think this makes a good manager, I want to do more of that, and I think these were terrible managers or bad managers and I want to avoid doing that? Do you remember some things that stuck out?
Yeah, I tried to really understand each individual person. So, for example, one person that I had on my team really loves going deep into problems or debugging and finding out how to improve things, right? Whereas another person really loves building new features. And you cannot ask this person who loves to build new features to go debug 10 bugs; that person will go nuts, right? And then one person who was really good at building new features was not so great at mentoring new colleagues. So, I try to really look for their strengths, and of course you also want to set them up for challenges so they can learn as well, but you want to balance them out. So, I try to really understand by asking them a lot of questions: how do they want to be challenged? When do they feel excited about their work? What are the things that they're really good at? What are the things they want to improve on? So, I spent a lot of time really talking to them.
As a manager, you were part of calibration meetings, right? Now that you're not at WhatsApp, not at Meta, can we talk honestly about what those meetings are like? What are maybe the good things about them? How can you prepare? And what's the kind of reality? Because I feel outside of a small group of managers who are in there, not many people know how these things go.
So, the number one biggest mistake people make is they think your manager is the one giving you a promotion or a salary boost. Like, as a manager, a middle manager, right? I have no authority to give you a promotion.
You have no budget. Typically directors have a discretionary budget and are sometimes able to give a reward, but not even a promotion can they give, right? Right. And the bonuses are tied to your performance review, right? So at Meta, for every level there's exact percentages lined up by the comp team. I have no control over it. The only control I have is I think of myself as the lawyer representing my clients.
Wow, yeah. I'm making a case for them. Yeah. Why they deserve to get a certain performance review rating or a promotion. And obviously I want my clients to do well. I want my team to get, you know, the recognition that they deserve, because I know they worked hard. But it's not up to me. All the other managers also have to agree. That is the
the nature of performance reviews. And being specific on a performance review, like who were the people that you saw, the engineers who got these high performance reviews from this committee? What kind of tactics did you see? Were there things like, well, some managers kind of like, you know, politics where they're calling in favors for each other and pushing someone up, or was it mostly meritocracy, meaning this engineer was actually doing great work that a lot of managers saw and they just naturally agreed that, you know, this person who's on Jean's team, they should be above my great person, and I kind of agree with that? Because there's bucketing, right? Like let's say there's bucketing, you're going to have buckets and you need to put like, I don't know, X people in the top bucket, middle bucket, bottom bucket, and so on.
Yeah, when I was coaching engineers, I learned that different companies have different ways of self-promotion. So, like for example, I heard some companies use emails. Like, they send mass emails every time they do a new release or launch. Or like at WhatsApp, we use WhatsApp groups for everything. But at Facebook, they used Facebook Workplace, which is like Facebook groups where you have a group for your team or your org and everything has a different group.
And I noticed as I'm representing my clients during performance reviews, the people who post the most often, who have the most visibility, usually get the easiest consensus. Because it's just all very natural. Like, if I have no clue what you worked on and your manager tells me you're great, maybe, but how would I know? I don't know anything about you. So I'm less likely to be inclined to agree with your manager. Maybe your manager's right, but I don't know. Whereas, if you have been actively posting and telling me indirectly or directly what type of work you have done and what type of impact that has made and what are the lessons that you've learned and what type of people you work with, then I already know, "Oh, okay." Like, when your manager tells me you're ready, then I say, "Yeah."
Internally, this was actually more than just groups. It was like this Facebook feed where, you know, it's a bit like LinkedIn, right? So you see these posts come across the company and sometimes you'll put a like, and what you're saying is if you've seen this post from this engineer on some other team saying, "Oh, we've launched this feature. Here's an interesting thing we've learned that we're using for Facebook." And I hit like, I now remember it. And then when performance review comes, I go, "Oh, I remember that person. They wrote that."
Exactly. And I might even have some questions, right? Maybe if your manager tells me, I might be like, "Well, what about this? What about that?" But if you make a post, I can just ask you directly through the comments, right? There's a lot of engagement happening in the comments. So, I might ask, "Have you thought about this other thing? Have you thought about this thing?" And you might give me answers, and I think, "Oh, okay. Yeah, he's thought about it. He's really good."
It's amusing because it sounds like, simplifying a little bit, to be successful at Facebook, you need to also be good inside of the Facebook app and do interesting work and not hide it. Actually, make it visible. Mhm. That's interesting. Now, stepping a step back, you were a manager at Facebook, you saw a lot of engineers. Outside of the performance you had and people posting about it, what traits did the best engineers that you remember share? Like, what made them so good?
I struggle with this question a little bit because there's a difference between... Like, how do you measure skill? How do you measure what a good engineer is? Is a good engineer someone who can bang out new features? Is a good engineer someone who can design a complicated system? Is a good engineer someone who can communicate all of this and explain it to non-technical people? I struggle a little bit with the definition of a good engineer because I can have a definition of a good engineer, but it may be different for every culture. A different company might have different definitions.
A good one. At Facebook, what was the definition? I remember that a lot of it went down to just a very simple characteristic, impact, right?
Definitely. And I think there are many ways to measure impact, and definitely at Facebook their way of measuring impact was through these posts. If I know about your work and you tell me you have impact, and I agree that's impact.
So, going back to when you were in the London office and the startup grew, at what point did the London office start to feel less of a scrappy startup and more of a big tech?
I remember a time after about a year and a half or so, I realized I don't know who that person is, or I don't know their name. That was a turning point.
Mhm. And at what point did you actually start to think of leaving Facebook?
I think I really enjoyed the intimate environment. So, I appreciate being able to, like at WhatsApp with 30 engineers, I knew everyone's names, I knew where everybody lived, I knew their spouses and their children and their dogs' names, right? I really like that type of intimate environment. We still hang out and we have a pretty strong bond. And I feel like even when I don't even know this person's name, I just feel less connected.
Yeah. So, was this the point where you decided that maybe it's time for you to leave and do something else?
Also, okay, I was in London on a contract. So, I had a 2-year contract. They said, "Hey, go start this office." And then once the contract ended, I had the option to either stay there to continue working in the London office or I could come back to Menlo Park. But then at that point I had been working there for 8 years and honestly I think I was pretty burned out. I'm the type of personality who likes to get A+ on everything I do every single time. Yeah. So, it was pretty tiring after 8 years. I needed a break.
Yeah. And when you left WhatsApp, what did you decide to do? Well, I say WhatsApp, but it was Facebook at that point.
Yeah. I actually, because I know my personality, I don't take breaks. So, I actually had a goal. It's so simple, but I said, "I will do nothing for the next 6 months. I'm going to challenge myself to do nothing for 6 months."
Did you manage?
I did it. I did it. I did read a lot. I exercise. I went on long walks. I did multiple meditation retreats. But that was my challenge to myself, to not work for 6 months.
So, after 6 months of successfully doing nothing, after setting yourself that goal, what did you do to figure out what next?
So, initially I thought maybe I want to go start a new company or join another startup because I like working. I love building things. So, I decided okay, I'm going to start talking to other founders or people who are hiring or people who are looking to start a new company. So, I actually talked to 100 founders. I have a spreadsheet. Wow. To really see if there are any interesting opportunities that I might feel passionate about joining or building. And then after talking to 100 startups, I realized I wasn't really passionate about joining any of them.
And I thought, what would I feel more passionate about, and what was the thing that I liked the most about working at WhatsApp for the past 8 years? And I realized I actually really liked being a manager because I felt like I was creating a culture of support so that other people can really be learning and thriving and, you know, be able to do things freely without people breathing down your neck. There are many things that make for a happy career, but I found it really gratifying to be able to find that from each person and really try to help them out and create whatever that is. It might be different for different people, and trying to unblock them so they can really flourish. And I thought, well, if that's what I really want to do, I don't have to start a new company. I'll just do that part. So, I started exploring mentoring people. I did a little bit of coaching, I don't do it anymore, and making videos on YouTube, writing, all of that to see how would I find the best way to support other people?
And on YouTube and on LinkedIn you have been sharing a lot of your learnings, your observations. What pushed you to just start sharing way more of that than before? I think you started to do this publicly after you left Facebook.
I was actually writing a blog about this. So I actually just hit 100k subscribers on YouTube like last week. Thank you. And I was reflecting, I almost gave up doing YouTube because I was really not comfortable being seen in public. And I've been thinking a lot about this, like my grandma's from North Korea. She escaped during the war, and in that culture you do not speak publicly. You don't want to be seen because it's dangerous. And I think there's generations of that still kind of installed in me. The fear of speaking up is real. I felt really uncomfortable. So I almost stopped doing YouTube.
Once one of my videos went viral early on and I felt really uncomfortable. But luckily I was talking to a mentor of mine and she said, "Hey, it's okay to do something that you enjoy doing. Just give it a shot." So then I stuck with it. I'm so glad I did.
Speaking of the thing that is happening, of course, right now: AI. You spoke about this on your YouTube channel as well. But from your vantage point, how is AI changing how engineers work, how managers work?
I do find it really interesting how with AI we're seeing smaller teams emerge. I know that a lot of teams are saying, "Well, we're small because of AI." But I wonder if it's independent from AI. When you're small, you're just more efficient. Because WhatsApp did not use AI. But we were efficient because we were small.
And I almost feel that even today I cannot really point to too many teams that are as small as WhatsApp and have that kind of impact. Maybe Anthropic might come to mind, but I think even they're bigger. So I wonder if there is maybe just going back to basics with all of this. Maybe AI allows to do the way most companies would have wished they operated.
Yeah, and I think there's also a shift in the mindset. Like I remember back in the days, when you go to networking events, people would brag about, "Oh, we've hired like a thousand new engineers," or "We're growing X times bigger." And that was a point of brag. And investors also thought that was a good thing. You need to grow. You need to hire more engineers. That was a sign of a healthy engineering environment. Whereas nowadays investors actually think smaller is better, right? They don't necessarily push you to hire more people. And I think as a byproduct of hiring fewer people and staying lean, they have found this newfound efficiency and they happen to equate it with AI.
Although AI, I think it's clear it makes engineers a lot more efficient in... well, we think it makes them efficient because it can generate a lot of code. You can work on more things in parallel, as is happening with agents. How are you seeing the role of software engineers change and also the role of engineering managers?
Yeah, I mean I love AI tools. I use it every day as a thought partner. I often ask ChatGPT, "Hey, be my executive coach," or "Be a Harvard-trained futurist and then help me find the next trends." Or, you know, there are various ways of really using AI to its full potential. I feel like engineering management is less affected by AI because it requires a lot of people-to-people, like asking questions and learning about your engineers. AI can maybe help you with that, but I don't see AI replacing that part. But again, because the teams are much smaller, if you are the type of engineering manager who was doing a lot of this OKR and process and writing documentation, a lot of that part is going to be gone. And I'm kind of glad it will be gone because I don't think it's really necessary.
Yeah, for example, a lot of performance management, you know, gathering the impact, it can probably be done by asking agents to gather all these things. I remember as an engineering manager, I used to go through gathering all the work that my engineers had done, so in the calibration meeting I could fairly represent them. And then it turns out that over the managers who showed up without doing that, I had an advantage. But that was not fair for the engineers, by the way, right? Maybe AI will get rid of this advantage.
Yeah, AI will do a lot of the grunt work, more tedious work that maybe engineering managers or even software engineers had to do manually back in the days. Like we had an engineer who was just there to add comments. And that is something AI can do really well.
If you had to give career advice to a new grad who says, "I would like to build a durable career in software engineering in this kind of AI-native world, what would you suggest they focus on?"
I'd say foundations. You know, tools come and go, languages come and go, but foundations don't go anywhere.
We mentioned that WhatsApp was very small, very efficient. What do you think today's AI or AI-native startups could still learn from WhatsApp? That made WhatsApp successful and it probably helped them as well.
I think of AI... so, we went through several trends. Like when I first got my first internship, the first I ever had was at a video sharing website, and I've seen how there were dozens of video sharing websites and how the ecosystem changed over time. And then I saw with WhatsApp there were dozens of other messaging app competitors and how that kind of settled down over time. I think we're living through something similar. There are so many new AI startups and new tools, and it's so easy to get distracted by all the different options and it can feel quite overwhelming. There are too many options and you can feel the decision paralysis. But really, again, go back to the core foundation. Think about, if you're a builder, think about what you're building, why you're building. If you're learning, think about why you're learning, what you want to learn. And if you have clear goals of where you want to go, it will really ground you, because otherwise you're just going to be all over the place and you might work really hard and end up nowhere.
Did I understand correctly that you're saying that WhatsApp was successful because the goal was clear? Jan said no to the distractions and all the ideas, but was very thorough in watching, whereas all the other competitors, even all the messaging apps, they got distracted building, "Oh, let's do all this cool video feature. Let's do stories. Let's do all of these things." They got some traction and they did a lot of these things, but WhatsApp was very good at doing the core thing well and then slowly adding things that were value added. Is that a fair summary?
Yeah. And also I noticed this when I started advising and coaching startup founders as well. And also for any engineers who want to join new startups, this is a great way to evaluate new founders. Like some founders, if you're the opposite of Jan and say no to things... I call it removing distractions, right? You're prioritizing ruthlessly. If you're the opposite of that, imagine what type of startup you end up with. You say yes to everything. Maybe it might feel really nice as a 20-something-year-old if I were to go back in time and I go to the founder with all my great ideas and he says, "That's a great idea, Jean. Let's build it." But imagine he said that to every single idea that I had, the company would be all over the place. In terms of the long-term growth, it's not a very ideal situation.
So, looking back, what are some kind of pre-AI or not-as-modern practices that you did at WhatsApp that were really good that today's very modern AI-native teams or whoever could benefit from?
Yeah, several things come to my mind.
I think one of it is by having lean teams, you get several benefits. You get to remove a lot of the distractions in process, and through that you get two really incredible benefits, which is ownership and the really, like, the freedom to build things. Right? Because Jan and Brian were always very specific about what we're building. But how we're building it was up to debate, right?
I had mentioned earlier that the only time we did an actual code review was the first time I made my Git commit. Brian reviewed my code and asked me a bunch of questions. So, Jan and Brian were both so technically adept, they were really excellent at doing this. They would ask, "We're trying to achieve this. Like, what is the problem here? Or what is the best way to solve this issue? What are different ways we can approach this? Tell me."
So do I understand correctly that of course the small teams helped with a lot of things, but then having the founders push people they hire, especially early on, they almost push them to excellence, right? Is it fair to say that by Brian doing that super detailed code review with you the first time, it upped your game, and later he didn't even have to do anything, right?
Yeah, and it's multi-fold, right? Like, one is to really challenge me to think critically, and I learned a lot just from that conversation. And then also, from then on he never checked my code again. So I know I am responsible, right? And I do believe when you give responsibilities to people, people will step up. Maybe not everyone.
But most people will. But I think this might be a bit underrated. I wonder if we've had a little bit of too much over-babying of engineers. I remember for a long time there was a talk in the past 5 to 10 years, as engineering managers, like, "Well, I have a new grad. It will take them months to onboard. I need to assign them a mentor for at least 6 months, maybe even a year." And were we over-babying these very capable adults? You know, they're adults, right? Even if they're 18, but they're typically 20-something because they came out of college, and they're hungry and they're ambitious, and maybe we don't need to do this much of it always.
Yeah, I think as long as you hire smart people, it's kind of like a mold, right? If you make a mold too small, that's the limit of how far they will grow. If the mold is too small, you have to throw away a lot of things that could have made excellent material.
And finally, you're a reader. What are some books that you would recommend for software engineers or people wanting to grow professionally or in a personal sense?
I love reading books. So while I challenged myself to do nothing, I actually took a year, but I did read 100 books during that time. That was my doing nothing. Anyways, it kind of depends on what your goals are, but you gave me some specific things. Like for your career, I think for me what was really helpful was What Color Is Your Parachute? That helped me really understand my strengths and my goals and priorities in my career and life. I mentioned the book Surrounded by Idiots. I know the title's kind of funny, but it's an excellent book if you want to learn more about how to really communicate and work with different people. If you want to understand finance, I mentioned earlier A Random Walk Down Wall Street. It's a great book for understanding how to manage your money. Yeah, I would recommend those books to start with.
Any fiction books?
Hunger Games was one of my favorite books. I read the whole series.
I read it as well, and I like the movies as well, but I love the books.
Yeah, yeah. I love the story of this woman overcoming her challenges, and everyone else, and winning in the end. Several times.
Well, Jean, thank you so much.
Yeah, thank you. Thank you for having me on the channel. This was a great conversation.
I hope you enjoyed this rare conversation with Jean. One thing that stuck with me was Jean's point about why WhatsApp had almost no process and why it worked. Processes exist for audits, for accountability, and for tracking who did what. But when you have 30 people and everyone can see what everyone else is working on, you don't really need a paper trail. You just walk over and talk. This is a good reminder that most processes exist to solve problems that are created by scale and not by the work itself.
I found the Skype contrast really surprising. A thousand engineers, Scrum certifications, two-week sprints, and a dedicated Scrum Master for every team. I was one of them at Skype. And WhatsApp, with 30 people and zero formal methodology, was shipping faster and growing faster on every metric that mattered. This is a much-needed reminder that organizational discipline and actual shipping speed are just not the same thing. And I was in the middle of this at Skype, and Jean was in the middle of it at WhatsApp.
Finally, it was interesting, as a former manager, to hear how Jean described performance reviews as a manager herself. She described herself as a lawyer representing her clients. As in, she doesn't control the promotion, she just makes the case. And the engineers who had the easiest time getting promoted were not necessarily the best engineers. They were the ones who made their work visible. They posted about their launches in the internal Facebook Workplace. They engaged in comments, answered questions publicly, and the managers in those calibration rooms are making decisions about people that they might have never worked with directly. So, visibility is not just vanity. It's how the system inside larger companies actually works. This is an uncomfortable truth, but I think every engineer at a big company needs to hear it.
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