Prometheus

The monitoring system that watches your systems so you don’t have to (but you still will, at 3 AM). Prometheus is a time-series database and monitoring toolkit that scrapes metrics from your services at regular intervals.

It uses a powerful query language called PromQL that’s somewhere between SQL and arcane incantations. Once you master it, you can slice and dice your metrics in ways that make dashboards actually useful.

Why it matters: Prometheus is the de facto standard for Kubernetes monitoring. If your cluster isn’t being scraped by Prometheus, does it even exist?