Deployment strategy using two identical environments where you switch traffic from old version to new version instantly. Like having two identical stages where you prepare the new show while the old one is running.
You deploy the new version to the 'green' environment, test it thoroughly, then instantly switch all users from 'blue' to 'green' with zero downtime.
Blue-green deployment is a deployment pattern, not a single managed service. It’s commonly implemented using each cloud’s load balancers/traffic routing plus separate compute environments (VMs, containers, or serverless) and an automated release pipeline.