Why are you comparing PostgreSQL to an in-memory SQLite instead of a file-based one? Wow, memory is faster than disk, who would have thought?
Running 100,000 `SELECT 1` queries:
PostgreSQL (localhost): 2.71 seconds
SQLite (in-memory): 0.07 seconds
SQLite (tempfile): 0.07 seconds
I hope you understand that your claim boils down to stating that SQLite is faster at doing nothing at all, which is a silly case to make.
Running 100,000 `SELECT 1` queries:
PostgreSQL (localhost): 2.84 seconds
PostgreSQL (Unix socket): 1.93 seconds
SQLite (in-memory): 0.07 seconds
SQLite (tempfile): 0.06 seconds