AWS Certified SysOps Administrator – Associate (SOA-C03) — Question 43

An application runs on Amazon EC2 instances behind an Application Load Balancer (ALB). The application takes up to 2 minutes to populate a local cache after the application is started. The application reports as healthy in the target group health check a few seconds after starting.
A CloudOps engineer observes that after some of the instances are rebooted, the instances receive an equal share of the traffic immediately after each instance reports as healthy. The application needs to receive a gradually increasing share of the traffic while the application cache is populated.
Which solution will meet this requirement?

Answer options

• A. Change the slow_start.duration_seconds target group attribute to 120 seconds. Before rebooting the instances, deregister the instances from the target group. After rebooting the instances, register the instances with the target group.
• B. Change the HealthCheckTimeoutSeconds paramotor in the target group to 120 seconds. Before rebooting the instances, deregister the instances from the target group. After rebooting the instances, register the instances with the target group.
• C. Configure an Amazon CloudWatch alarm to monitor the health check status. Configure the action of the alarm to restart an EC2 instance if a health check fails. Change the loadbalancing.algorithm.type target group attribute to be weighted_random.
• D. Create an Amazon EC2 Auto Scaling group. Attach the existing EC2 instances to the Auto Scaling group. Configure an EC2 Auto Scaling lifecycle hook to move starting instances to the Pending Wait state. Update the application to complete the lifecycle hook when the local cache has been populated.

Correct answer: A

Explanation

The correct answer is A because adjusting the slow_start.duration_seconds attribute allows for a delayed traffic allocation to the newly rebooted instances, which gives the application time to populate the cache. Options B and C do not address the gradual traffic increase requirement, while D introduces unnecessary complexity with Auto Scaling and lifecycle hooks when a simpler solution exists.