What is blue-green deployment?

Question

Accepted Answer

**Blue-Green** — **two environments** (blue and green).

```yaml
# Kubernetes Blue-Green
apiVersion: v1
kind: Service
metadata:
  name: app
spec:
  selector:
    app: myapp
    version: blue
  ports:
    - port: 80
      targetPort: 3000
---
# Switch to green
kubectl patch service app -p '{"spec":{"selector":{"version":"green"}}}'

# Rollback to blue
kubectl patch service app -p '{"spec":{"selector":{"version":"blue"}}}'
```

**Advantages:**
- Instant rollback.
- Zero downtime.
- Testing in production.

**Disadvantages:**
- Duplicate resources.
- Complex data synchronization.

DevOps: What is blue-green deployment?