PAS-C01 Technology Practice Question
A company is running SAP BusinessObjects on AWS. The application is deployed on EC2 instances with an Application Load Balancer. Users are reporting that the application is sometimes unreachable. What is the most likely cause?
⚠ Common exam trap
Candidates often confuse intermittent reachability with misconfigured security groups or DNS, but the key phrase 'sometimes unreachable' points directly to a dynamic health check failure rather than a static configuration error.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The target group health checks are failing intermittently on the EC2 instances.
Intermittent unreachability of an application behind an Application Load Balancer (ALB) is most commonly caused by health checks failing on the target EC2 instances. When health checks fail intermittently, the ALB will periodically mark the instances as unhealthy and stop routing traffic to them, causing the application to become unreachable during those windows. This matches the symptom of 'sometimes unreachable' rather than a persistent failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The target group health checks are failing intermittently on the EC2 instances.
Why this is correct
Unhealthy instances are removed from the load balancer, causing connection failures.
- ✗
The security group for the instances is not allowing traffic from the load balancer.
Why it's wrong here
If misconfigured, it would be consistently unreachable, not intermittent.
- ✗
The load balancer is not configured with sticky sessions.
Why it's wrong here
Sticky sessions affect session persistence, not availability.
- ✗
The Route 53 TTL is too short for DNS resolution.
Why it's wrong here
Short TTL causes more DNS queries but not unavailability.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PAS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PAS-C01 exam.