It's Friday evening. An endpoint that normally answers in 200 milliseconds is suddenly taking eight seconds. You open Grafana. Every graph is green. CPU is calm, memory is fine, the disk isn't full. By every dashboard you have, the database is healthy.
It is not healthy.
This is the failure mode monitoring is worst at: the server is unmistakably alive, so nothing alerts, while inside the database something is slowly rotting. A table has bloated. An index nobody uses is dragging down every INSERT. A forgotten transaction is sitting open, holding a lock and quietly making everything worse. None of it crashes. It just degrades, a little at a time, until one Friday evening it tips over.
The good news is that Postgres will tell you all of this — you just have to ask. The queries below run on bare PostgreSQL (13 or newer; one version note along the way), need no agent and no paid monitoring, and use an extension in exactly one place where it genuinely earns it. Open psql and check your own database as you read.
1. The cheapest signal: dead rows
