Here's one specific one, I would imagine they have a pretty big user base: https://tailscale.com/blog/database-for-2022/

Here are a few other sources I googled:

https://www.sqlite.org/famous.html

https://stackshare.io/sqlite

This is the best I can do, because I have no idea what else you want. If I had the time, I could throw up a simulated million users doing a TODO app with SQLite as the backing DB engine, but I don't have time, I have a 2 year old. Do your own research from here, or don't and just use Postgres until you retire, I don't really care that much.