AWS Certified Developer – Associate — Question 119

A developer deploys an ecommerce application on Amazon EC2 instances behind an Application Load Balancer (ALB). The instances run in an Amazon EC2 Auto Scaling group. The EC2 instances are based on an Amazon Machine Image (AMI) that uses an Amazon Elastic Block Store (Amazon EBS) root volume. After deployment, the developer notices that a third of the instances seem to be idle. These instances are not receiving requests from the load balancer. The developer verifies that all the instances are registered with the load balancer. The developer must implement a solution to allow the EC2 instances to receive requests from the load balancer.

Which action will meet this requirement?

Answer options

• A. Reregister the failed instances with the ALB.
• B. Enable all Availability Zones for the ALB.
• C. Use the instance refresh feature to redeploy the EC2 Auto Scaling group.
• D. Restart the EC2 instances that are not receiving traffic.

Correct answer: B

Explanation

The correct answer is B because enabling all Availability Zones for the ALB allows it to distribute requests across all registered instances in those zones, potentially resolving the issue of idle instances. Options A and D do not address the underlying issue of Availability Zones, while option C, although useful for redeployment, does not directly resolve the load balancing problem.