Observability
The ability to understand a running system from its outputs (logs, metrics, traces) so you can debug and operate it.
Definition
Observability is how well you can understand a running system by looking at what it emits.
At minimum, that means logs, metrics, and traces.
Why it matters
If you cannot see what the system is doing, you will not be able to operate it under failures.
What you should be able to answer
- Is the system up or down.
- Where time is spent.
- What changed recently.
- Which dependency is slow.
Relationship to reliability
Observability is how you protect reliability over time.
If you cannot debug quickly, incidents last longer.