When to reach for a trace

Understanding why a system behaves the way it does by looking at the data it produces is called observability. That data comes as four signals: metrics, logs, traces, and profiles. Monitoring tells you when a known problem happens; observability helps you understand why, including problems you didn’t predict. Tracing is one of the four signals.

What each signal answers

The question only a trace answers

Reach for a trace when the question is “where did the time go across services?” That’s the service-to-service timing no other signal reconstructs. A metric tells you checkout is slow, a log tells you one service recorded an error, and a trace tells you which hop in the checkout path lost the time.