What is Blue-Green Deployment?
Blue-green deployment runs two identical production environments — one live (blue) and one staging the next release (green). You switch traffic from blue to green instantly, enabling zero-downtime releases and fast rollbacks.
In plain English
Imagine two identical bridges crossing a river. While cars drive across the blue bridge, crews quietly finish paving the green bridge. When it's ready, you flip a sign redirecting traffic to green — instantly and safely. If green has a crack, you flip the sign back.
How it works
You deploy your new version to the idle environment and run tests against it while it receives no user traffic. When you're satisfied, you update the load balancer or DNS to point to the new environment — the switch takes seconds. The old environment stays live as a fallback until you're confident the new one is healthy.
Why it matters for AI-built apps
AI-generated code can introduce subtle bugs that only appear under real production load. Blue-green deployment gives you a quick escape hatch: if users start hitting errors after a deploy, you roll back in seconds rather than re-deploying a fix. It removes the terror of deployment day.
Best practices
Ensure both environments share the same database schema — database migrations must be backward compatible with both blue and green code. Smoke test the green environment with synthetic traffic before switching. Keep blue live for at least 30 minutes after switching so rollback is still instant if needed.
Frequently asked questions
How is blue-green different from canary deployments?
Blue-green switches 100% of traffic at once for an all-or-nothing cutover. Canary gradually shifts a small percentage of traffic to the new version, letting you catch issues with limited blast radius.
Is blue-green deployment expensive?
It doubles your server costs during the transition window — typically minutes to an hour. For most apps the risk reduction is worth the temporary cost.
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