AWS Certified DevOps Engineer – Professional (DOP-C02) — Question 304

A company's web application uses an Application Load Balancer (ALB) to direct traffic to Amazon EC2 instances across three Availability Zones.

The company has deployed a newer version of the application to one Availability Zone for testing. If a problem is detected with the application, the company wants to direct traffic away from the affected Availability Zone until the deployment has been rolled back. The application must remain available and maintain static stability during the rollback.

Which solution will meet these requirements with the MOST operational efficiency?

Answer options

• A. Disable cross-zone load balancing on the ALB's target group. Initiate a zonal shift on the ALB to direct traffic away from the affected Availability Zone.
• B. Disable cross-zone load balancing on the ALB's target group. Manually remove instances in the target group that belong to the affected Availability Zone.
• C. Configure cross-zone load balancing on the ALB's target group to inherit settings from the ALB. Initiate a zonal shift on the ALB to direct traffic away from the affected Availability Zone.
• D. Configure cross-zone load balancing on the ALB's target group to inherit settings from the ALB. Remove the subnet that is associated with the affected Availability Zone.

Correct answer: A

Explanation

To successfully execute a zonal shift on an Application Load Balancer (ALB), cross-zone load balancing must be disabled on the target group so that traffic does not get routed back to the affected zone from other active zones. Using Route 53 Application Recovery Controller (ARC) zonal shift provides the most operationally efficient and automated way to redirect traffic during an incident. Options involving manual removal of instances or subnets introduce significant operational overhead and increase the risk of downtime or configuration errors.