How about DuckDB: https://duckdb.org/ https://duckdb.org/ It keeps databases in a single local file like SQLite, and it supports PostgreSQL syntax (not sure w

How about DuckDB: https://duckdb.org/ https://duckdb.org/ It keeps databases in a single local file like SQLite, and it supports PostgreSQL syntax (not sure which version). It does a load of funky stuff to be really fast at analytics workloads, but I would guess it's fast enough at transactional workloads for small-scale use.