Yup. Entire core business product for a succeeding startup, though it's a small team of contributors (<10), and a much smaller platform team. Serverless backend started in 2018. Been a blessing in many regards, but it has its warts (often related to how new this architecture is, and of course we've made our own mistakes along the way).

I really like the model of functions decoupled through events. Big fan of that. It's very flexible and iterative. Keep that as your focus and it's great. Be careful of duplicating config, look for ways to compose/reuse (duh, but definitely a lesson learnt) and same with CI, structure your project so it can use something off-the-shelf like serverless-compose. Definitely monorepo/monolith it, I'd be losing my mind with 100-150 repos/"microservices" with a team this size. If starting now I'd maybe look at SST framework[0] because redeploying every change during development gets old fast

I couldn't go back to any other way to be honest, for cloud-heavy backends at least. By far the most productive I've ever been

Definitely has its warts though, it's not all roses.

[0] http://sst.dev