Postgres is much heavier than SQLite in terms of binary size/CPU/RAM, but I think scalability is the win.

OTOH if you don't tune it the default postgres configuration remains extremely low-resource (which also hampers its performances): 128MB shared buffers, 8MB temp buffers, 4MB work_mem, 64MB maintenance_work_mem, 100 connections, 1000 files open.

Compared to less than 1MB for sqlite in this use case.