Your application is currently running on Amazon EC2 instances behind a load balancer. Your management has decided to use a Blue/Green deployment strategy. How should you implement this for each deployment?

Answer options:

A.Set up Amazon Route 53 health checks to fail over from any Amazon EC2 instance currently being deployed.
B.Using AWS CloudFormation, create a test stack for validating the code, and then deploy it to each production Amazon EC2 instance.
C.Create a new load balancer with new Amazon EC2 instances, carry out the deployment, and then switch DNS over to the new load balancer using Amazon Route 53 after testing.
D.Launch more Amazon EC2 instances to ensure high availability, de-register each Amazon EC2 instance from the load balancer, upgrade it, test it, and then register it again with the load balancer.

Answer – C
The below diagram shows how this can be done.
1) First, create a new ELB which will be used to point to the new production changes.
2) Use the Weighted Route policy for Route53 to distribute the traffic to the 2 ELB’s based on a 80-20% traffic scenario. This is the normal case; the % can be changed based on the requirement.
3) Finally, when all changes have been tested, Route53 can be set to 100% for the new ELB.Option A is incorrect because this is a failover scenario and cannot be used for Blue-green deployments. In Blue-Green deployments, you need to have 2 environments running side by side.
Option B is incorrect, because you need to have a production stack with the changes which will run side by side.
Option D is incorrect because this is not a blue-green deployment scenario. You cannot control which users will go to the new EC2 instances.
For more information on blue-green deployments, please refer to the below document link: from AWS
https://d0.awsstatic.com/whitepapers/AWS_Blue_Green_Deployments.pdf