The answer is failing target group health checks, which cause the ALB to mark SAP Web Dispatcher instances as unhealthy and return 503 errors. When the Application Load Balancer cannot route traffic to any registered targets because their health checks are failing, it has no healthy backend to serve the request, resulting in a 503 Service Unavailable response. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of ALB error codes in the context of SAP Web Dispatcher high availability—a common trap is confusing 503 with 504 errors (which indicate timeouts from blocked security groups) or 502 errors (which point to SSL certificate mismatches). The key distinction is that 503 always signals an unhealthy target, not a network or encryption issue. Memory tip: think "503 = zero healthy targets" to quickly eliminate other options.
PAS-C01 Operations and Maintenance Practice Question
This PAS-C01 practice question tests your understanding of operations and maintenance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs its SAP landscape on AWS and uses an Application Load Balancer (ALB) to distribute traffic to multiple web dispatchers. The operations team notices that some requests are failing with 503 errors. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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, causing the ALB to mark instances as unhealthy.
Option C is correct because 503 errors typically indicate that the target instances are unhealthy or the ALB cannot route traffic to them. Option A is wrong because security groups blocking traffic would cause 504 or timeout errors. Option B is wrong because SSL certificate issues cause 502 errors. Option D is wrong because CloudFront is not in the path.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 groups for the ALB are blocking incoming traffic.
Why it's wrong here
Blocked traffic would result in connection timeouts, not 503.
The CloudFront distribution in front of the ALB is misconfigured.
Why it's wrong here
No CloudFront mentioned in the scenario.
✓
The target group health checks are failing, causing the ALB to mark instances as unhealthy.
Why this is correct
503 errors occur when no healthy targets are available.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Scenario analysis trap
No CloudFront mentioned in the scenario.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PAS-C01 NAT questions on configuration and troubleshooting.
Operations and Maintenance — This question tests Operations and Maintenance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The target group health checks are failing, causing the ALB to mark instances as unhealthy. — Option C is correct because 503 errors typically indicate that the target instances are unhealthy or the ALB cannot route traffic to them. Option A is wrong because security groups blocking traffic would cause 504 or timeout errors. Option B is wrong because SSL certificate issues cause 502 errors. Option D is wrong because CloudFront is not in the path.
What should I do if I get this PAS-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PAS-C01 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs SAP on AWS and uses an Application Load Balancer (ALB) to distribute traffic to web dispatchers. The operations team notices that some requests are failing with 503 errors. What is the MOST likely cause?
medium
A.The SSL certificate on the ALB has expired.
B.Security groups allow too much traffic.
✓ C.The target instances are failing health checks.
D.The ALB is out of capacity.
Why C: Option C is correct because 503 errors from an ALB indicate that the target instances are unhealthy or not responding. Option A is wrong because 503 errors are not caused by SSL certificate issues. Option B is wrong because security groups would cause connection timeouts, not 503. Option D is wrong because ALB capacity is automatically scaled.
Last reviewed: Jun 20, 2026
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.