Observability

Three signals that answer three different questions — logs: what happened; metrics: how much and how often; traces: where did this request spend its time — each with its own cardinality and cost profile, and none of which can substitute for the other when the p99 doubles at 3 a.m.

Follow one request Browser → Gateway → Service A → Service B → Database as a tree of timed spans stitched together by a propagated trace id, so that fan-out, serial-versus-parallel calls and the 140 ms of database time hiding behind an N+1 become visible in a way no log search can reproduce.