SQLite is a real database
It is not a toy. For read-heavy applications with a single writer it is faster than a networked database because there is no network. The limitation is concurrent writes, not scale of data.
MySQL for familiarity, PostgreSQL for correctness
MySQL is everywhere, every host supports it and every developer has used it. PostgreSQL has stricter types, better JSON support, real check constraints and window functions that make reporting queries far simpler.
The question that decides it
Who will maintain this in two years? A database your team can operate confidently beats a technically superior one nobody wants to touch.
