The answer is an intermittent 500 status code from the health check endpoint. This is correct because ALB 503 errors from health check failures occur when the load balancer determines that all registered targets are unhealthy, stopping traffic routing. If the /health endpoint returns a non-2xx response, even briefly, the ALB marks those instances unhealthy after the configured threshold of two consecutive failures, causing the 503 error for users. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how health check thresholds interact with target health status—a common trap is confusing the health check grace period (which only applies during instance launch) with ongoing health monitoring. Remember that 503 always means no healthy targets, not a timeout or performance issue. A useful memory tip: "503 means zero healthy; check the health endpoint's response, not the grace period."
SOA-C02 Networking and Content Delivery Practice Question
This SOA-C02 practice question tests your understanding of networking and content delivery. 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's web application uses an Application Load Balancer (ALB) in front of multiple EC2 instances in an Auto Scaling group. Users report intermittent 503 errors. The ALB health checks are configured to check the /health endpoint every 30 seconds with a threshold of 2 successful checks to mark healthy. The Auto Scaling group’s health check grace period is set to 60 seconds. What is the most likely cause of the 503 errors?
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 health check endpoint is returning a 500 status code intermittently.
Option A is correct because 503 errors from an ALB typically indicate that all targets are unhealthy. If the health check endpoint returns a non-2xx status for even a short period, the ALB will stop routing traffic to those instances, causing 503 errors. Option B is wrong because if the application is not responding, the health check would fail, but the symptom is 503, not timeout. Option C is wrong because the health check grace period only applies during instance launch. Option D is wrong because a small instance type would cause performance issues, not necessarily health check failures.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 ALB’s idle timeout is set too low.
Why it's wrong here
ALB idle timeout affects persistent connections, not health checks.
✗
The Auto Scaling group health check grace period is too short.
Why it's wrong here
Grace period only delays health checks during instance launch, not after.
✗
The EC2 instances are of a small instance type and are overloaded.
Why it's wrong here
Overloaded instances could cause latency but not necessarily health check failures.
✓
The health check endpoint is returning a 500 status code intermittently.
Why this is correct
Intermittent health check failures cause targets to be marked unhealthy, leading to 503 errors.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Networking and Content Delivery — This question tests Networking and Content Delivery — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The health check endpoint is returning a 500 status code intermittently. — Option A is correct because 503 errors from an ALB typically indicate that all targets are unhealthy. If the health check endpoint returns a non-2xx status for even a short period, the ALB will stop routing traffic to those instances, causing 503 errors. Option B is wrong because if the application is not responding, the health check would fail, but the symptom is 503, not timeout. Option C is wrong because the health check grace period only applies during instance launch. Option D is wrong because a small instance type would cause performance issues, not necessarily health check failures.
What should I do if I get this SOA-C02 question wrong?
Identify which SOA-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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