If your app has a slow endpoint and you're staring at application logs trying to guess which query is the culprit, stop. Postgres already tracked every query it ran, how long each one took, and how often — you just haven't asked it yet. pg_stat_statements is a built-in extension that turns "something feels slow" into "this exact query, called 40,000 times a day, is burning 60% of your database's CPU." Fifteen minutes from now you'll have a ranked list of your worst offenders and a fix for the top one.
Step 1: Turn it on (2 minutes)
pg_stat_statements ships with Postgres but isn't loaded by default. It needs to be in shared_preload_libraries, which means a config change and a restart — this is the one part of this technique you can't do without a brief window of downtime or a failover if you're on a managed HA setup.
Check if it's already loaded:
SHOW shared_preload_libraries;
