This. So much this. Of course, at one point you start wanting to do queues, and concurrent jobs, and not even WAL mode and a single writer approach can cut it, but if you've reached that point then usually you a) are in that "this is a good problem to have" scalability curve, and b) you can just switch to Postgres.

I've built pretty scalable things using nothing but Python, Celery and Postgres (that usually started as asyncio queues and sqlite).

A queue and a database are more shots on the architecture golf though.