Performance

How database connection pool exhaustion happens under production load, how to distinguish pool wait from slow SQL, and how to size pools across instances without overloading PostgreSQL.

A production workflow for finding slow SQL queries, reading EXPLAIN plans, choosing fixes, and proving the endpoint improved.

How to detect and fix the N+1 query problem in ORMs with query counts, SQL traces, eager loading, batched IN queries, request-scoped loaders, and production rollout checks.

Why adding more service instances can leave throughput flat when the bottleneck is a shared database, lock, connection pool, external dependency, queue, cache, or load-balancing constraint.

Why read replicas often fail to reduce primary database load when reads are coupled to writes, replica lag triggers fallback behavior, and query cost is misunderstood.