For a new application, the DevOps team is implementing a blue/green deployment strategy. For each new release, the application can be deployed via a CloudFormation stack, including resources such as Auto Scaling Group, Launch configuration, and Classic Load Balancer. A weighted routing policy is configured in Route53. With Route53, a small percentage of traffic goes to the green environment, and the weights increase until the green environment carries the full production traffic. However, which disadvantage may this approach have?

Answer options:

A.A weighted routing policy is complicated to implement in a pipeline.
B.DNS TTL decides how long clients cache query results. Certain sessions may still be tied to the previous environment to impact the speed to deploy a new environment or rollback.
C.Route53 weighted routing policy is not suitable if a rollback is required.
D.Only a Classic load balancer is suitable for this approach. A network load balancer or application load balancer cannot be used together with the Route53 weighted routing policy.

Correct Answer – B
To implement blue/green deployments in AWS, there are several methods. For the details, check the document in
https://d1.awsstatic.com/whitepapers/AWS_Blue_Green_Deployments.pdf.
In this scenario, the deployment strategy is as below:
Option A is incorrect: On the contrary, DNS weighted routing in Route 53 is simple to implement for blue/green deployment.
Option B is CORRECT: This limitation is clearly indicated in the above link. Older clients may take a long time until they use the new environment.
Option C is incorrect: Because for rollback, it is quite straightforward by switching back the weight to the old environment.
Option D is incorrect: Because a Network load balancer or application load balancer can also be used together with Route53 weighted routing.