Metrics vs Logs vs Traces: A 2026 Decision Guide

Each telemetry type has a sweet spot. The decision tree that picks the right type per use case, with cost and cardinality trade-offs.

When metrics win

Aggregate questions: 'how is the service performing overall?' Pre-aggregated, cheap, fast to query.

Cardinality is the limit. Metrics with too many label values become expensive; convert to logs.

When logs win

Specific questions: 'what happened to this one request?' Structured logs answer quickly.

High cardinality is fine; cost is volume not cardinality. Tune log levels in production to manage volume.

When traces win

Cross-service questions: 'where in the chain did this slow down?' Traces show the dependency graph in motion.

Sample wisely. 100% sampling is expensive; tail-based sampling captures slow traces while saving cost on fast ones.