midDevOps
Prometheus Metrics vs Logs vs Traces.
Updated Apr 28, 2026
Short answer
These are the three pillars of observability. Metrics are numerical data over time, Logs are immutable discrete events, and Traces follow a request across distributed systems.
Deep explanation
Metrics (Prometheus) answer 'Is there a problem?' (e.g., CPU is at 99%). Traces (Jaeger/OpenTelemetry) answer 'Where is the problem?' (e.g., Request spent 2 seconds in the Auth service). Logs (Elasticsearch/Loki) answer 'What exactly is the problem?' (e.g., NullPointerException at line 42).
Real-world example
Getting an alert from Grafana that latency has spiked (Metrics), using a Trace ID to see the database query took too long (Trace), and checking the DB logs to find a missing index error (Log).
Common mistakes
- Logging absolutely everything and ignoring metrics, resulting in massive log storage costs and slow alerting.
Follow-up questions
- What kind of data model does Prometheus use?