Observability (Prometheus + Grafana) via Docker Compose

A ready-to-run stack lives in deploy/compose/metrics: - app – FastAPI demo exposing /metrics using prometheus_client.generate_latest() - prometheus – scrapes app:8000/metrics - grafana – UI at http://localhost:3000 (admin/admin by default)

docker compose -f deploy/compose/metrics/docker-compose.yml up --build
open http://localhost:8000/docs
open http://localhost:9090
open http://localhost:3000

Prometheus best practices: prefer Histograms for latency, choose buckets thoughtfully; when changing buckets, use a new metric name and keep the old during the transition to preserve history.