AWS Certified SysOps Administrator – Associate (legacy) — Question 138

A SysOps Administrator created an Application Load balancer (ALB) and placed two Amazon EC2 instances in the same subnet behind the ALB. During monitoring, the Administrator observes HealthyHostCount drop to 1 in Amazon CloudWatch.
What is MOST likely causing this issue?

Answer options

• A. The EC2 instances are in the same Availability Zone, causing contention between the two.
• B. The route tables are not updated to allow traffic to flow between the ALB and the EC2 instances.
• C. The ALB health check has failed, and the ALB has taken EC2 instances out of service.
• D. The Amazon Route 53 health check has failed, and the ALB has taken EC2 instances out of service.

Correct answer: A

Explanation

The correct answer is A because having both EC2 instances in the same Availability Zone can lead to resource contention, which may affect their performance and health status. Options B, C, and D do not directly relate to the HealthyHostCount issue, as they involve different configurations and checks that would not inherently cause a reduction in healthy hosts in the same subnet scenario.