What are the three pillars of observability (metrics, logs, traces)? [Basic]
Answer
The three classic pillars are metrics, logs, and traces. Metrics show numeric trends over time, logs provide event-level detail, and traces show the path and timing of a request across services.
Technical explanation
Metrics are low-cardinality time series, good for alerting, capacity planning, SLOs, and trend analysis.
Logs are discrete records, good for explaining a specific event, error, state transition, or audit trail.
Traces connect spans from multiple services so we can see where time was spent and which dependency caused delay or failure.
Hands-on example
Example: a payment timeout appears as an elevated p95 latency metric, the trace shows checkout spent 1.8 seconds in payment-authorize, and the payment logs for the trace_id show an upstream gateway timeout. The three signals together give both scope and root-cause evidence.
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