An application release model known as "blue green deployment" gradually moves user traffic from one version of an app or microservice to another, both of which are already in use in the real world.
Blue-Green Deployment Strategy:
Such a deployment strategy produces blue and green infrastructure environments, which are distinct from one another. A green environment (production) has the most recent code, while a blue environment (old version) contains older code (new version). At any given time, there is only one live production environment.
For Example: A program has two clones; the blue clone is idle while the green environment is active and handling all user traffic. An application can be deployed to the blue environment for testing once a new version is ready for release.
A switch is made from green to blue in the application traffic as soon as the new release passes testing. Green becomes vacant and ready for testing the following release, while Blue becomes the active production environment.
Rolling Deployment Strategy
By completely replacing the infrastructure they run, old versions of an application are completely replaced with new versions using this deployment strategy.
For Example: When a new version needs to be deployed to all nodes, the first node receives it while the other nodes manage end-user traffic. The new version will start controlling end-user traffic as soon as the first node has successfully installed it, and the second node will follow suit. The procedure is repeated until all nodes have successfully upgraded to the new version.