Rolling update:
- Gradually replace old pods with new
- Simple, built into Kubernetes
- Risk: bad version serves traffic during rollout
Blue-green:
- Two identical environments (blue and green)
- Deploy to inactive, switch traffic
- Instant rollback (switch back)
- Cost: double infrastructure
Canary:
- Deploy to small subset of users (-%)
- Monitor metrics, expand if healthy
- Catches issues before full rollout
Interview question: "Design a deployment strategy for a payment service."
Canary with strict health checks. Start at % traffic, monitor error rates and latency, expand gradually. Keep rollback ready.