Database Indexing Best Practices for Growing Apps

An index that speeds up one query can slow down writes elsewhere, so indexing is always a tradeoff rather than a free performance win.

The most common mistake we see is indexing columns that are rarely filtered on while ignoring the ones actually used in WHERE clauses and JOIN conditions. Composite indexes, ordered to match your most frequent query patterns, usually deliver more benefit than many single-column indexes.

We review slow query logs early in performance audits, since a handful of well-placed indexes often resolves issues that teams initially assume require a hardware upgrade.