Blue-Green Deployment

A deployment strategy that maintains two identical production environments (blue and green), switching traffic from the active environment to the newly deployed one, enabling instant rollback if the new version has problems.

Blue-green deployments eliminate downtime during releases and provide a safety net against bad deployments. If the new version has a critical bug, traffic is switched back to the old environment in seconds rather than requiring a complex rollback procedure.

A founder's team deploys a major new version of her app to the green environment while blue serves all user traffic. After automated tests confirm green is healthy, traffic switches to green in under a minute. When a critical bug surfaces three hours later, traffic switches back to blue instantly with no user disruption.