Blue-Green Deployment Cheat Sheet

Patterns for running two identical production environments to enable zero-downtime releases and instant rollback.

1 PageAdvancedFeb 12, 2026

Core Concept

How blue-green deployments work at a high level.

Blue environment- The currently live production environment serving all user traffic
Green environment- An idle, identical environment where the new version is deployed and validated
Traffic switch- A router/load-balancer/DNS change that instantly cuts traffic over from blue to green
Rollback- Simply switch traffic back to blue if green shows errors post-cutover
Smoke tests- Automated checks run against green before it receives real traffic
Database compatibility- Schema changes must be backward-compatible so both blue and green can operate against the same DB during transition

Kubernetes Example

Switch a Service's selector to cut over traffic.

yaml

# Service currently points at the 'blue' DeploymentapiVersion: v1kind: Servicemetadata:  name: myappspec:  selector:    app: myapp    version: blue   # change to 'green' to cut over  ports:    - port: 80      targetPort: 8080

Cutover & Rollback

Scripted traffic switch and rollback commands.

bash

# Deploy green alongside blue, then verify it's healthykubectl apply -f green-deployment.yamlkubectl rollout status deployment/myapp-green# Cut traffic overkubectl patch service myapp -p '{"spec":{"selector":{"version":"green"}}}'# If green is unhealthy, roll back instantlykubectl patch service myapp -p '{"spec":{"selector":{"version":"blue"}}}'

Pro Tip

Keep the blue environment running (not torn down) for a defined soak period after cutover — instant rollback is only instant if the old environment is still warm and ready to receive traffic.

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