Zero-Downtime Production Release & Verification Checklist

# Zero-Downtime Production Release Checklist

## 1. Pre-Flight Verification (T - 24 Hours)
- [ ] **Database Migration Backward Compatibility:** Verify all schema migrations are non-breaking (expand-and-contract pattern).
- [ ] **Automated CI Test Suite:** 100% pass rate across unit, integration, and E2E Playwright test suites.
- [ ] **Artifact Signatures:** Verify container images are signed and scanned with Trivy (zero Critical/High CVEs).
- [ ] **Secret Rotation & Environment Parity:** Staging and Production secret versions aligned in HashiCorp Vault.
- [ ] **Rollback Plan Documented:** Verified single-command revert commit and database down-migration scripts.

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## 2. Deployment Cutover (T - 0)
- [ ] **Canary Routing Activation:** Route 5% of production ingress traffic to the new release pod group.
- [ ] **Real-Time Telemetry Inspection:** Monitor Datadog / Prometheus for 10 minutes:
  - Error rate < 0.01%
  - P99 API Latency < 45ms
  - CPU / Memory utilization within nominal baseline (< 60%)
- [ ] **Traffic Ramp-up:** Increment traffic progressively: 5% -> 25% -> 50% -> 100%.

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## 3. Post-Deployment Verification (T + 30 Minutes)
- [ ] **Synthetic Smoke Tests:** Automated headless browser smoke test suite executed against production endpoints.
- [ ] **Background Worker Verification:** Queue consumer lag is zero across all Kafka partition topics.
- [ ] **Log Stream Health:** Sentry error count stable with zero unhandled exception regressions.
- [ ] **Release Sign-off:** Lead Architect signs off and archives deployment audit log.