Deployment Automation Tools —
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Manual Rollback Strategy (Jenkins, GitHub Actions, GitLab CI)
Re-deploy the previous image tag to production. Requires immutable image naming — never use latest. Tag images with git SHA or semantic version: app:v1.2.3 or app:abc1234. To rollback: trigger deployment with previous tag. Reliable control: maintain a deployment history log. Drawback: 5-10 minute rollback time. Best for: non-critical services, development/staging environments.

Blue-Green Deployment (Kubernetes, AWS Elastic Beanstalk, Octopus Deploy)
Maintain two identical environments: Blue (current production) and Green (new version). Deploy new code to Green, run smoke tests, then switch traffic via load balancer or service selector. Rollback: switch traffic back to Blue in seconds. Cost: requires double infrastructure. Advantage: instant, zero-downtime rollback — most reliable for critical services. Implementation: Kubernetes with two Deployments + Service label selector switch, or Nginx upstream switch.

Canary Deployment with Automated Rollback (Argo Rollouts, Flagger, Harness)
Route small percentage of traffic (5% → 25% → 50% → 100%) to new version. Monitor error rates, latency, business metrics. Rollback automatically if metrics breach thresholds. Advantage: catches issues affecting small user base before full rollout. Requires: observability setup (Prometheus, Datadog). Tools like Harness offer AI-powered anomaly detection for auto-rollback. Most reliable for high-frequency deployments (10+ per day).

GitOps Rollback (ArgoCD, Flux for Kubernetes)
Git repository is single source of truth. Deployment = Git commit changing image tag in manifest. Rollback = revert Git commit, ArgoCD auto-syncs cluster to previous state. Advantage: full audit trail, all changes reviewed via PRs, automatic drift detection. Most reliable for Kubernetes. Implementation: update image tag in deployment.yaml, commit, ArgoCD detects diff and reconciles in seconds.

Automated Health-Check Rollback (Kubernetes, AWS CodeDeploy, Harness)
After deployment, run health checks (HTTP, custom scripts, Kubernetes liveness/readiness probes). If checks fail, automatically revert to previous version. Kubernetes native: set maxUnavailable: 0, configure readiness probes, use progressDeadlineSeconds for auto-rollback. Advantage: zero manual intervention. Reliable for stateless apps. Drawback: requires robust health check logic.

Rolling update — simplest, most common
Replaces instances one by one (or in batches). Zero-downtime if done correctly. Rollback: re-deploy the previous image. Risk: mixed versions run simultaneously during rollout — ensure backward compatibility in APIs and database schemas. Kubernetes RollingUpdate deployment strategy does this natively. Set maxUnavailable: 0 and maxSurge: 1 for true zero-downtime rolling.

Blue-Green deployment — safest, highest cost
Maintain two identical environments: Blue (current) and Green (new version). Deploy to Green, run smoke tests, then switch traffic (via load balancer or DNS). Rollback: switch traffic back to Blue in seconds. Cost: requires double the infrastructure. Best for: critical services where instant rollback is required. AWS Elastic Beanstalk, Kubernetes with two Deployments + Service switch, or Nginx upstream switch.

Canary deployment — gradual rollout
Route a small percentage of traffic (e.g., 5%) to the new version. Monitor error rates, latency, and business metrics. Gradually increase traffic (5% → 25% → 50% → 100%). Rollback: reduce canary traffic to 0%. Tools: Kubernetes with Argo Rollouts or Flagger, AWS CodeDeploy canary, NGINX split_clients. Requires good observability — you need metrics to know when to proceed or rollback.