Monitoring tells you when something is wrong. Observability helps you understand why.
Monitoring collects predefined metrics. You decide what to watch in advance. If you did not set up monitoring for something, you will not see it.
Observability goes deeper. A system is observable if you can understand its internal state from its outputs.
Three pillars of observability:
- Metrics tell you what is happening
- Logs tell you what happened
- Traces tell you how requests flow through your system
Start with monitoring. Add observability as your systems grow complex.