So I am a big believer in sqlite -> And for a time I thought I would want to set up a file per user. However over time I have come round back to the idea that for now a server based database solution is better suited to write heaver operations when it comes to user data.

For that reason most of the read heavy data such as blogs and content are served through SQLite and the client based data is served through postgres. I use UUID's to keep both databases in sync with each other, though it is a loose sync and is mostly seperate.

The reason I have opted for Postgres and Sqlite over Mysql is because Mysql doesn't offer any advantages over SQLITE or Postgres.