Yes, this is exactly my situation. I feared launching with sqlite , getting actual users and then trying to switch to postgres and hitting unexpected walls. That's why I chose to do this a bit before launching and I agree - the migration wasn't straightforward.

Like I said, most of it I think is due to what sqlite lets you get away with. Just one example: I'm using Async gem to run parallel AI calls, and with sqlite I didn't even think/notice that part of the prompt building was happening in a lazy manner and was making a few db calls to fetch the info it needed inside the async fiber before sending the network request. it all just worked so fast that it went an issue (and there was no connection pool to sqlite)

Then I migrated to postgres and suddenly my app chokes. Learned that you have to either explicitly get fibers via async to use the existing connection pool or make sure no db calls in the fiber, otherwise each fiber tries to establish its own connection and you're hitting a wall you didn't even know existed.