PostgreSQL Autovacuum Tuning: A Practical Guide

PostgreSQL Autovacuum Tuning: A Practical Guide If you've ever stared at a PostgreSQL table wondering why queries got slower over time even though the data hasn't changed much, there's a decent chance autovacuum is the culprit. Not because it's broken -- because its defaults are tuned for safety, not for your workload. Most teams never touch the autovacuum config, and for small tables that's fine. But once your tables grow past a few million rows, the defaults start working against you. Let's walk through what's actually happening and how to fix it. The Problem Autovacuum is PostgreSQL's background process for reclaiming dead tuples, updating planner statistics, and preventing transaction ID wraparound. It runs automatically, and for many databases the defaults work well enough that you never think about it. The problems start when they don't -- and the symptoms are often misdiagnosed. When autovacuum falls behind, dead tuples accumulate, tables bloat, queries slow down as they scan th