| name | monitoring |
| description | Application monitoring, logging, and observability for production applications. Use when: setting up error tracking, adding logging, creating health endpoints, configuring alerting, preparing for production, or when debugging production issues. |
Monitoring
Overview
Monitoring turns invisible failures into visible signals. The goal is knowing when something breaks before users do.
1. Structured Logging
Use JSON format with consistent fields across all log entries.
Required fields: timestamp, level, message, request_id
Useful fields: user_id (not PII), service_name, duration_ms, status_code
Log levels:
error — Something failed and needs attentionwarn — Degraded state but still functioning (slow query, retry succeeded)info — Important business events (user signup, payment processed)debug — Development detail — never in production
Never log: Passwords, API keys, tokens, session secrets, PII (emails, addresses).
2. Error Tracking
Configure Sentry, LogRocket, or Bugsnag. Capture stack traces, group by root cause, alert on new error types. Tag errors with release version for regression detection.
3. Health Endpoints
/health — Liveness check. Returns 200 if the process is running. Used by load balancers.
/ready — Readiness check. Verifies dependencies: database, cache, external APIs. Returns 503 if any dependency is down.
4. Uptime Monitoring
External ping service (UptimeRobot, Pingdom, Better Stack) hits /health every 1–5 minutes from multiple regions. Alert on 2+ consecutive failures.
5. Alerting Strategy
Page (immediate): 5xx error rate spike, health check failure, database unreachable.
Notify (review soon): Slow response times (p95 > threshold), elevated error rate.
Avoid alert fatigue: Every alert should have a clear action. If you ignore an alert regularly, fix it or remove it.
Key Metrics
| Metric | Target |
|---|
| Response time p95 | < 500ms |
| Error rate (5xx / total) | < 0.1% |
| Uptime | 99.9%+ |
Common Rationalizations
| Rationalization | Reality |
|---|
| "We'll add monitoring when we need it" | You need it the moment a real user touches your app. |
| "Console.log is fine" | Console.log in production is noise. Structured logging is signal. |
| "Dashboards are enough" | Nobody watches dashboards at 3am. Alerts catch what dashboards miss. |
Verification
