PAS-C01 Operations and Maintenance Practice Question
A company has an SAP system running on AWS that uses an Application Load Balancer (ALB) to distribute traffic to multiple EC2 instances. The operations team notices that the ALB is returning 503 errors intermittently. Which of the following is the MOST likely cause?
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 instances are failing health checks.
503 errors are typically returned when the target instances fail health checks and become unhealthy. Option A is wrong because if the security group blocked inbound traffic from the targets, it would cause timeout or 502 errors, not 503. Option C is wrong because insufficient ALB capacity can lead to latency or 502 errors, but 503 specifically indicates unhealthy targets. Option D is wrong because an expired SSL certificate would result in 502 errors (bad gateway), not 503.
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 security group attached to the ALB is blocking inbound traffic from the targets.
Why it's wrong here
Incorrect. If the security group blocked inbound traffic from the targets, it would cause timeout or 502 errors, not 503.
- ✓
The target instances are failing health checks.
Why this is correct
Correct. 503 errors are typically returned when the target instances fail health checks and become unhealthy.
- ✗
The ALB does not have enough capacity to handle the traffic.
Why it's wrong here
Incorrect. Insufficient ALB capacity can lead to latency or 502 errors, but 503 specifically indicates unhealthy targets.
- ✗
The SSL certificate on the ALB has expired.
Why it's wrong here
Incorrect. An expired SSL certificate would result in 502 errors (bad gateway), not 503.
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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.