I like the idea of SQLite, even more with tools like Litestream [0] when the database is replicated - in this case, just continuously backup to S3 (and from S3 during startup). I found often for my and my friend's hobby projects, single server instances can be optimized easily enough to handle small and medium traffic. In such cases, I don't even bother with a fully managed database because SQLite covers all the needs and when it's located on the same machine as the server is extremely fast [1].

[0] https://litestream.io/ [1] https://www.sqlite.org/speed.html