blue/green deploy
also: blue-green deployment, blue/green release, red/black deployment
A deployment strategy where two identical production environments (blue and green) run in parallel, allowing you to switch traffic between them instantly to minimize downtime and enable quick rollbacks.
Blue/green deployment maintains two separate, identical production environments. At any time, one environment (say 'blue') serves live traffic while the other ('green') remains idle or runs the previous version. When deploying a new release, you update the inactive environment, run tests, then switch the load balancer or router to direct traffic to it.
This approach eliminates deployment downtime because the switch is instantaneous. If the new version has critical bugs, you can instantly redirect traffic back to the other environment while you investigate. For example, you might deploy a new application version to the green environment, verify it works, then update your load balancer to send requests to green instead of blue.
Blue/green differs from rolling deployment (updating instances one at a time) and canary deployment (gradually shifting traffic to new versions). It requires double the infrastructure but provides the fastest, safest switches between versions.