The choice between SQLite and PostgreSQL is a frequent point of confusion. The quick choice is: For almost any public-facing web app or SaaS, you want PostgreSQL. SQLite is for embedded, local-first, or very low-traffic internal tools. Here is a detailed breakdown across all relevant aspects for common web apps and then specifically for SaaS. Part 1: Common Web Apps (e.g., blog, small e-commerce, corporate site) For a typical web app with concurrent users (even just 10-50), the differences are stark. Aspect PostgreSQL SQLite Concurrency Excellent. Handles hundreds of simultaneous writes and thousands of reads via MVCC (Multi-Version Concurrency Control). Poor. Entire database is locked for writes. Reads are blocked during a write. Works for < 10 concurrent writes/sec. Write Scaling Multiple writers can work simultaneously, thanks to row-level locking. Only one writer at a time . If two users submit a form at the same second, one fails with database is locked .…