Blue-Green Deployment
A deployment strategy that maintains two identical production environments (blue and green), where one serves live traffic while the other is updated and tested. Traffic is switched from the old version to the new version all at once.
In a blue-green deployment, the 'blue' environment runs the current production version. The new release is deployed to the idle 'green' environment, where it is tested and validated. Once confirmed ready, the load balancer or DNS is switched to route all traffic from blue to green. If problems arise, traffic can be switched back to blue immediately.
This approach provides near-instant rollback capability and eliminates downtime during deployments. The tradeoff is the cost of maintaining two full production environments and the complexity of managing database migrations that must work with both versions.
Why It Matters for QA Teams
Blue-green deployments give QA teams a fully warmed-up production environment to validate before any real user is affected, and provide instant rollback if post-switch issues are found.
Example
The current production version runs on the blue environment. A major release is deployed to the green environment, where QA runs the full smoke suite and verifies critical user journeys. Once approved, traffic is switched to green. Two hours later, a critical bug is discovered. The operations team switches traffic back to blue within seconds while the QA team and developers investigate.