Blue-Green Deployments

A blue-green deployment runs two complete copies of the production environment side by side. Blue serves live traffic. Green runs the new version. When green is ready, the system flips traffic from blue to green in one step, with blue staying online as a hot standby for fast rollback.

The strategy trades infrastructure cost for rollback speed: a blue-green rollback is a traffic decision that takes seconds, vs minutes for rolling. For services where short outages are expensive, that difference is the entire point of the strategy.