Go Join the Startup

Why work at a startup + some takeaways from Brex

Julia Wu
6 min readAug 24, 2022

A lot of my friends seem to be thinking about career moves lately or are considering new opportunities. I hope that sharing a bit of my rationale and learnings during almost 3 years at a breakout startup can be helpful to those considering similar paths.

How it happened for me

Before Brex, I started my engineering career at Apple (Siri). In late 2017, I was catching up with an extremely talented friend who said fascinating things about a new credit card company called Brex. It turns out that some of the brightest, most driven people of my generation — including my friend — were part of this founding team.

When an insanely talented group of people come together to make something happen, you just can’t ignore it. I couldn’t help but wonder what it would be like to be part of this “mafia.” In the coming months, I would start to see more and more of Brex in the media and on San Francisco’s billboards. I decided I had to be part of it — especially since I wanted to start a company someday.

I joined Brex in August 2019, when the engineering organization was about 50 people. Little did I know that there would only be about 7 months of in-person experience until the pandemic changed everything.

I started out on the Expenses team, taking on the receipts matching feature. I remember learning Elixir for the first time while becoming the point-person for troubleshooting customer support tickets for this feature. A few months later, I was a core engineer building our first external API for ERPs like Quickbooks to integrate with Brex.

After some time on Expenses, I was curious about Card Infrastructure. I became the second engineer on the Card Fraud team and worked on enabling dispute-filing on the dashboard, as well as automated fraud alerts to bring more safety to our users while reducing operational costs. This was also my first experience as a Tech Lead/Manager, and my first time recruiting others to join our engineering team. I got to support engineers who were much more senior and skilled than myself while learning from them.

From Card Fraud, I went on to spin up the Card Growth and Rewards engineering teams as an Engineering Manager —while being mentored by managers across the company. It was a lot of growth (company and personal) packed into a couple of years, as I watched Brex go from 200 to nearly 1000 by early 2022.

Choosing the startup to join

Betting on a startup as an employee is, in many ways, similar to thinking like a venture capitalist. I am not a VC but if I were one, I would put a lot of emphasis on the team.

The people at Brex were a remarkable mix of intellectual curiosity and ownership. I’d never seen anything like it, despite having experienced a very competitive college environment, and worked at a couple of tech giants. There’s something extremely meaningful about being the dumbest person in the room and learning through osmosis. They say you’re the average of the 5 people you spend the most time with. Here, it wasn’t just 5 people that inspired me — it was everyone around me.

If you take one thing away from this post: Go after people who blow your mind in terms of intellect and integrity, who happen to be building something very big. They will inspire you to grow, and you will want to be your best self and end up creating value for those around you. Of course, you will also get to learn about the business and in the best-case scenario, be part of a generational company in its early days. But even if the startup doesn’t work out, you will still have learned and grown substantially if you got the people right.

Some Personal Lessons


  1. As a company, always be working towards a big goal together. This is powerful in rallying the team and bringing the company together in a unified mission.
  2. Set key metrics and track them obsessively on a regular basis. Be transparent and honest about how the company is doing. The good thing about having a very clear metric (i.e. GMV) is that you can align everyone and it’s super clear when we’re doing well vs. not. Always show charts, month-over-month growth, etc. on a regular basis
  3. When you achieve something that you previously thought was almost impossible or really hard, you experience unprecedented personal growth. Especially when you do that with a group of people.
  4. The effectiveness of written decisions (DACI framework), especially in a remote world.
  5. Treating employees like adults with transparency builds a lot of trust.
  6. It is more effective to increase value prop and reasons to buy, than to only rely on minimizing cost
  7. Brex is in the business of rethinking financial products. See the treasure chest in the Engineering blog
  8. Customer love is manifested through cross-functional collaboration in big initiatives. It’s Engineering/Product + Ops + CX + Marketing. Orgs learn from each other and are brought together by the goal of delighting the customer
  9. It’s not enough to have good intentions — you need a system that enforces it and makes sure you’re always executing (carrot and stick)


  1. Values: Dream Big, Inspire Customer Love, Impatient Optimism, One Brex, Growth Mindset, Ownership
  2. It is possible to be both kind/empathetic/humble and extremely ambitious
  3. At an early rocketship, there will be challenges. But owner’s mentality means that instead of blaming the environment, you have the ability and duty to make it better
  4. Everybody is a salesperson, and everybody is a recruiter. You do it automatically and not from a desire to be awarded something
  5. Values interviews are critical. Never budge on this. Values interviewers should be bar raisers for company culture
  6. Ownership is when you stop waiting for answers, and instead just execute towards the reality you want
  7. The spirit of requesting and giving feedback is everywhere, and it doesn’t always have to be anonymous
  8. Leaders should represent the company’s values. As a leader, you have the responsibility to embody the culture of the company — at a personal level
  9. One way to motivate really driven people is through big, challenging goals and problems. Show the progress we’re making to get there. Acknowledge it’s hard. And give ownership

Management & Personal

  1. Being a manager makes your heart grow bigger. The best managers are also very thoughtful and aware of their reports’ focus areas and output. They have their reports’ back and stand up for their team. They show off the work done by their reports. They are punctual. They follow up and follow through with their words.
  2. Praise in public, reprimand in private
  3. “I trust you, make the call” is an extremely powerful thing to hear from a supervisor
  4. Delegate until it hurts. This gives ownership to others, while also freeing you to do the highest leverage thing
  5. You will make mistakes and you will learn. Mistakes (especially public ones) make you humble too.
  6. If you can dream big and execute, the world is your oyster

Engineering & Product

  1. The highest impact features are not always the biggest technical challenges
  2. Demo a lot
  3. Praise and highlight invisible/infra work
  4. From The Effective Engineer: “I’ve found that almost all successful people write a lot of tools … [A] very good indicator of future success [was] if the first thing someone did on a problem was to write a tool.”
  5. Logging/tracing: Invest in observability as early as possible. It’s good for your systems and customers
  6. You never, ever regret writing documentation. What you think is easily remembered/taken for granted today is what you will thank yourself for jotting down tomorrow. Document all the things!
  7. Architecture docs & forums: Always include multiple options and describe their tradeoffs. Ultimately recommend one design though.

CTA for Women in Engineering

I’ll conclude this post with a message to women in tech. :)

If you’re a female engineer debating whether to join a startup, do it. We need more representation at early-stage tech startups, and there is a lot of learning and impact to be made. You might find yourself being a torchbearer for culture and D&I — but do the very technical stuff too, and keep working on your craft. Being an engineer is a superpower.

And for those who want to start a company: also do it (at least, try). Peter Thiel said something interesting: “if we want to have more women in tech, it is not enough to get more women engineers and executives — we need more women founders because it is the founders of companies that set the cultural tone for so much that happens in Silicon Valley.”

Some relevant communities are YC’s women in engineering initiatives, and Pear’s Female Engineer/Founder Circles.

The rocketship I got on taught me that dreaming big is a virtue. Proceed and be bold.



Julia Wu

Building something new. Prev. eng at Brex, Apple, MSFT. More at juliawu.me