Metrics (what is happening — trends/aggregates, e.g., Prometheus/Grafana), logs (what happened — discrete events, e.g., ELK/Loki), and traces (why it happened — a request across services, e.g., Jaeger). Together they let you investigate unknown failures.

Detailed Answer

Metrics quantify system state over time and drive alerts; logs give event-level detail for a component; distributed traces follow one request end to end to localize latency or errors across services. Correlating a trace ID into logs links them. Observability (explore unknown-unknowns) is broader than monitoring (watch known conditions).

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Interview Tip

Map each pillar to its question: metrics=what, logs=what happened, traces=why — and name a tool for each.

sreobservabilitymetricslogstraces

What are the three pillars of observability and what does each answer?

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