In blue-green model, two identical application stacks are maintained (for convenience, I will refer to our application server instances and service instances as a stack, database deployments are done separately .
One of the stack is always live, let us say green is live and blue is standby. When we want to deploy a new build to production, we deploy it on blue stack and do thorough testing.
Once new build seems to work fine, the blue stack goes live and green becomes standby. This helps us do a quick rollback if issues are identified during deployment or sanity check.
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