AWS Certified DevOps Engineer – Professional — Question 150

A DevOps engineer is using AWS CodeDeploy across a fleet of Amazon EC2 Instances in an EC2 Auto Scaling group. The associated CodeDeploy deployment group, which is integrated with EC2 Auto Scaling, is configured to perform in-place deployments with CodeDeplcyDefault.OneAtATime. During an ongoing new deployment, the engineer discovers that although the overall deployment finished successfully, two out of five instances have the previous application revision deployed. The other three instances have the newest application revision.

What is likely causing this issue?

Answer options

• A. The two affected instances failed to fetch the new deployment.
• B. A failed AfterInstall lifecycle event hook caused the CodeDeploy agent to roll back to the previous version on the affected instances.
• C. The CodeDeploy agent was not installed in two affected instances.
• D. EC2 Auto Scaling launched two new instances while the new deployment had not yet finished, causing the previous version to be deployed on the affected instances.

Correct answer: D

Explanation

The correct answer is D because if EC2 Auto Scaling launches new instances during an in-progress deployment, those new instances may receive the previous version of the application. Options A and C are incorrect as they imply a failure in fetching or installation that would not specifically explain the deployment of the previous version, while B discusses a rollback scenario that does not apply here as the deployment was still marked successful.