What deployment strategy allows for maintaining a previous version while switching all traffic to a new application version?

A blue/green deployment strategy is designed to minimize downtime and ensure a smooth transition when deploying new application versions. This strategy involves maintaining two identical environments, referred to as "blue" (the current version) and "green" (the new version). Initially, the blue environment serves all the production traffic. When you are ready to deploy a new version of the application, you provision it in the green environment.

Once the new version is tested and confirmed to be functioning correctly in the green environment, you can switch all traffic to the green environment with a simple change in the routing configuration. This switch allows for a seamless transition since the blue environment is still available and can be rolled back to in case any issues arise with the new version. This capability to maintain the previous version while simultaneously deploying and testing the new version is a key advantage of the blue/green deployment strategy, promoting higher application availability and reducing deployment-related risks.

The other deployment strategies, such as canary, rolling, and recreate deployments, each serve different purposes and have their own strengths. However, they either introduce risks during the transition (like in rolling or canary deployments) or require downtime for a complete replacement (as with recreate deployments), which is not the case with blue/green