What is the difference between Blue-Green, Canary, and Rolling deployments? When would you use each?

Question

Accepted Answer

Three deployment strategies with different trade-offs in risk, cost, and complexity . Blue-Green Deployment Two identical environments: Blue (live) and Green (new version). Deploy new version to Green, test, then flip traffic from Blue to Green at the load balancer. Pros: instant rollback (flip back). Cons: 2× infrastructure cost. Canary Deployment Roll out new version to a small % of users first (e.g., 1% → 10% → 50% → 100%), monitoring metrics at each step. Pros: real production signal at low blast radius; safe for risky changes. Cons: requires advanced traffic routing (Istio, Linkerd, Argo Rollouts) and good observability. Rolling Deployment Replace pods/instances gradually one batch at a time . Default for Kubernetes Deployments. Pros: no extra infra. Cons: slower rollback; mixed-version state during rollout. Pick by: risk tolerance (Canary safest) → cost (Rolling cheapest) → rollback speed (Blue-Green fastest). Frame your answer around blast radius and rollback speed. Blue-Green = full prod backup, instant rollback, double cost. Canary = gradual rollout, real-user signal, complex routing. Rolling = simplest, slow rollback. Don't forget to mention monitoring as the gating mechanism.