Q3 — AWS DOP-C02 Ch.2

Question 3 of 100 | ← Chapter 2

A company runs an application behind an Application Load Balancer (ALB) on Amazon EC2 instances located across multiple Availability Zones. The application experienced an outage due to misconfiguration in a single Availability Zone.

• A. Disable cross-zone load balancing on the ALB. Use Amazon Route 53 Application Recovery Controller to initiate regional failover from the affected Availability Zone. ✓
• B. Disable cross-zone load balancing on the ALB target group. Use Amazon Route 53 Application Recovery Controller to initiate regional failover from the affected Availability Zone.
• C. Create an Amazon Route 53 Application Recovery Controller resource set using the ALB's DNS hostname. Initiate regional failover from the resource set starting from the affected Availability Zone.
• D. Create an Amazon Route 53 Application Recovery Controller resource set using the ALB's target group ARN. Create a readiness check using the ELBv2 target health rule.

Correct Answer: A. Disable cross-zone load balancing on the ALB. Use Amazon Route 53 Application Recovery Controller to initiate regional failover from the affected Availability Zone.

Explanation

AWS load balancer cross-zone load balancing is enabled by default, allowing traffic distribution across all registered targets in all Availability Zones. Disabling this feature restricts traffic routing to targets only within the same Availability Zone. Combined with Amazon Route 53 Application Recovery Controller's regional failover capability, traffic can be fully redirected to healthy Availability Zones upon detecting failure. Option A correctly disables cross-zone load balancing at the ALB level—preventing traffic from reaching the failed zone—and uses Route 53 to perform failover. AWS documentation specifies that cross-zone load balancing is a load balancer-level setting. Option B modifies target group settings, which does not affect cross-AZ traffic distribution. Option C omits disabling cross-zone load balancing, so the failed AZ may still receive traffic. Option D's resource set and readiness check do not address immediate failover testing requirements.