observability-stacklisted

## Purpose Ensure every service can be debugged without reproducing issues live. ## Checklist - **Structured logging**: JSON output with timestamp, level, service name, request ID, and error context. No free-form text logs. - **RED metrics** (services): Rate (requests/sec), Errors (failed requests/sec), Duration (latency p50/p95/p99). - **USE metrics** (resources): Utilization (CPU/memory/disk %), Saturation (queue depth), Errors (device errors). - **Distributed tracing**: trace context propagated across service boundaries; traces sampled for high-traffic services. - **Alerting on symptoms**: page on user-facing impact (error rate spike, latency degradation), not infrastructure noise (CPU > 80%). - **Dashboards**: one dashboard per service showing RED metrics, key dependencies, and recent deployments. ## Expected output A service that emits structured logs, RED/USE metrics, and trace context from day one, with symptom-based alerting and a service dashboard.