SQLite is a great but complex software. In order to properly use it, you do need to read the documentations, guides and resources available at the official website. If you don't, you will shoot yourself in the foot.

In that sense, I have the impression SQLite is different from other database software. You can usually get by with Postgres or MySQL (after they are set up) without looking at their docs.

I spent several hours reading the SQLite docs. It wasn't wasted time: actually learning SQLite made me a better professional. But for those thinking of using it on their side (or main) project, definitely understand how it works and what are the trade-offs involved.

Now, to answer your question specifically: it depends on a few factors. You can have concurrent readers (wal). With newer developments (wal2 + begin concurrent), you can also have concurrent writes as long as they happen at different pages.

If you are blindly doing multi-threaded connections without understanding the implications, you also risk corrupting the database entirely.