Nothing beats the nimbleness, simplicity and speed of SQLite, but it is not a client/server database engine (although it is often used for that purpose due to

Nothing beats the nimbleness, simplicity and speed of SQLite, but it is not a client/server database engine (although it is often used for that purpose due to its speed). Firebird can be used as a proper client/server database engine. It supports static data types and stored procedures (unlike SQLite). It sits somewhere between SQLite and PostgreSQL. So it may be worth evaluating if you don't want the heft of PostgreSQL but need features missing from SQLite.