Blue-Green vs Canary Deploy
Compare blue-green and canary deployments. When is canary preferable?
Answers use simple, clear English.
Quick interview answer
Blue-green runs two full environments and switches traffic at once (easy rollback). Canary shifts a small % of traffic to the new version, watches metrics, then progresses — better for detecting rare bugs with less blast radius. Needs good observability and automated rollback.
Detailed answer
Blue-green runs two full environments and switches traffic at once (easy rollback). Canary shifts a small % of traffic to the new version, watches metrics, then progresses — better for detecting rare bugs with less blast radius. Needs good observability and automated rollback.
Real example & use case
Checkout service canaries 5% of traffic while watching error rate and p99 latency SLOs.
Pros & cons
Pros of canary: lower risk. Cons: longer, needs metrics. Blue-green: simple but doubles capacity briefly.