- A
The ALB's idle timeout is set too low.
Why wrong: Low idle timeout would cause connection resets, not 503 errors.
- B
The security group for the ALB does not allow inbound traffic on the listener port.
Why wrong: Security group was not changed, and if it were blocking traffic, all requests would fail.
- C
The ALB's target group health check settings are misconfigured.
Why wrong: Health check misconfiguration would cause persistent failures, not intermittent errors.
- D
The deployment removed the health check path from the application.
If the health check path is removed, health checks fail, causing targets to be marked unhealthy, and ALB returns 503.
Question 430 of 1,746
SAP-C02 ALB Health Checks Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. A key principle to apply: aLB Health Checks. 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 a production application on EC2 instances behind an Application Load Balancer. After a recent deployment, users report intermittent 503 errors. The CloudWatch metrics show that the ALB's 'TargetResponseTime' is within normal range, but 'RequestCount' has increased by 50%. There are no changes to the security groups. 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 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 deployment removed the health check path from the application.
Option D is correct because if the deployment removed the health check path from the application, the health checks would fail for any instance that was updated. Since the application runs behind an ALB, the target group health check would mark those instances as unhealthy, causing intermittent 503 errors as traffic is routed only to remaining healthy instances. Even if not all instances are updated simultaneously, the gradual roll-out could lead to periods where all instances become unhealthy temporarily. Option A is incorrect because a low idle timeout would cause timeout errors, not 503s. Option B is incorrect because security groups were not changed. Option C is incorrect because misconfigured health check settings would cause consistent failures, not intermittent.
Key principle: ALB Health Checks
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
Low idle timeout would cause connection resets, not 503 errors.
- ✗
The security group for the ALB does not allow inbound traffic on the listener port.
Why it's wrong here
Security group was not changed, and if it were blocking traffic, all requests would fail.
- ✗
The ALB's target group health check settings are misconfigured.
Why it's wrong here
Health check misconfiguration would cause persistent failures, not intermittent errors.
- ✓
The deployment removed the health check path from the application.
Why this is correct
If the health check path is removed, health checks fail, causing targets to be marked unhealthy, and ALB returns 503.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
ALB Health Checks
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates may confuse 503 errors with timeout or capacity issues. In this scenario, the normal TargetResponseTime and increased RequestCount suggest the load balancer is working, but targets are being marked unhealthy due to a missing health check path.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- ALB Health Checks
- 503 Service Unavailable
TExam Day Tips
- 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
ALB Health Checks
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 aLB Health Checks, then practise related SAP-C02 questions on the same topic to reinforce the concept.
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Continuous Improvement for Existing Solutions — study guide chapter
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FAQ
Questions learners often ask
What does this SAP-C02 question test?
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — ALB Health Checks.
What is the correct answer to this question?
The correct answer is: The deployment removed the health check path from the application. — Option D is correct because if the deployment removed the health check path from the application, the health checks would fail for any instance that was updated. Since the application runs behind an ALB, the target group health check would mark those instances as unhealthy, causing intermittent 503 errors as traffic is routed only to remaining healthy instances. Even if not all instances are updated simultaneously, the gradual roll-out could lead to periods where all instances become unhealthy temporarily. Option A is incorrect because a low idle timeout would cause timeout errors, not 503s. Option B is incorrect because security groups were not changed. Option C is incorrect because misconfigured health check settings would cause consistent failures, not intermittent.
What should I do if I get this SAP-C02 question wrong?
Review aLB Health Checks, then practise related SAP-C02 questions on the same topic to reinforce the concept.
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?
ALB Health Checks
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Last reviewed: Jun 20, 2026
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