YC has a small and mighty software team, and the work here has a kind of leveraged impact that you won't find elsewhere: instead of helping grow a single startup, you'll be building software that helps thousands of startups succeed.
We're a group of 10 engineers working on everything from YC's Admissions Software to Work at a Startup. Many of us are former founders who have a passion for startups. You'll learn a ton about how startups are built (all employees join the YC "dinners" and talks) and you'll use best practices from our team with deep experience from FB, Google, Twilio, Salesforce, and a myriad of other companies.
Our stack is pretty straightforward (Rails, React, Postgres), but the last three engineers have learned it on the job. True to YC advice, our product engineers talk to our customers pretty regularly (in our case, it's mostly founders) and ship fast. We also define our own roadmap. You won't be building software to scale to millions of users, but you'll be talking 1-1 with lots of founders to build stuff they need to help build and grow their companies, and that's a different kind of reward.
Lastly, we pay competitively (both in salary and stock-like benefits), offer reasonable work-life balance, and we're fully remote at this point.
If working on YC's software team and helping great startups sounds interesting at all, please email me at ryan AT ycombinator.com.