Sql

The query works fine in development with 1,000 rows. In production with 50 million rows it locks up the database for 3 minutes. One missing WHERE clause, one implicit type cast, one function wrapping an indexed column — and PostgreSQL ignores your index entirely.

You need to export 10 million rows. You paginate with OFFSET, fetching 1,000 rows at a time. The first batch takes 50ms. By batch 5,000 the offset is 5 million rows and each batch takes 30 seconds. The total job takes 6 hours and gets slower as it goes.

Month 1 — queries are fast. Month 6 — users notice slowness. Month 12 — the dashboard times out. The data grew but the indexes didn't. Finding and adding the right index is often a 10-minute fix that makes queries 1000x faster.

Page 1 loads in 10ms. Page 100 loads in 500ms. Page 1000 loads in 5 seconds. OFFSET pagination makes the database skip rows by reading them all first. Cursor-based pagination fixes this — same performance on page 1 and page 10,000.