Postgresql

Connection pool exhaustion is one of the most common and sneakiest production failures. Your app works perfectly at low load, then at 100 concurrent users it freezes completely. No errors — just hanging requests. Here's the full diagnosis and fix.

The N+1 query problem is responsible for more "why is my app slow?" investigations than almost anything else. It hides perfectly in development, then silently kills your database at scale. Here's exactly what it is, how to detect it, and every way to fix it.

Your query runs in 2ms in development with 1,000 rows. In production with 10 million rows, the same query takes 8 seconds. The database does a full table scan on every single request. Here's how to identify missing indexes, write efficient queries, and build a database that stays fast as data grows.