Observability Patterns (Logging, Tracing, Error Handling)

Quick Guide: Structured logging with Pino (debug/info/warn/error). Correlation IDs for request tracing. Sentry error boundaries in React. Attach user context after auth. Filter expected errors (404s). Create Axiom monitors for alerts.

<critical_requirements>

CRITICAL: Before Using This Skill

(You MUST include correlation ID in ALL log statements for request tracing)

(You MUST use structured logging with required fields: level, message, correlationId, timestamp)

(You MUST filter expected errors (404, validation) from Sentry to avoid quota waste)

(You MUST attach user context to Sentry AFTER authentication completes)

(You MUST use child loggers with context instead of repeating fields in every log call)