Blue Green Deployment
In plain terms
Releasing by switching traffic between two identical environments.
Going deeper
You run the current version (blue) and the new one (green) side by side, then flip traffic to green once it's verified. If something breaks, you instantly switch back, minimizing downtime and risk.
Under the hood
Needs double the infrastructure briefly and careful handling of database migrations and in-flight sessions; instant rollback is the key benefit.
Examples
Swapping load-balancer targets, AWS CodeDeploy, two identical environment stacks.
Think of it like...
Like a theatre with two identical stages: you set up the new act on the second stage, then swing the audience over, ready to swing back if it flops.