Deploying MERN Like a Pro: CI/CD, Blue-Green & Zero-Downtime

Why Pipelines Matter

Zero-downtime deploys need three things: a pipeline, a health signal, and a safe rollback.

Steps

1. Build your Docker image (multi-stage).

2. Run tests + lint + typecheck.

3. Push image to registry with immutable tags.

4. Roll out with blue-green or canary; switch traffic after healthcheck.

kubectl apply -f deployment.yaml
kubectl rollout status deploy/web

Health, Metrics, and Alerts

Expose `/health`, add Prometheus metrics, wire alerts for error budgets.