- A
The target instances have reached the maximum number of concurrent connections allowed by the application or operating system.
When the application's connection backlog is full, the ALB receives a 'connection refused' or timeout, resulting in a 503.
- B
The target instances do not have enough capacity to handle the request volume.
Why wrong: Insufficient capacity typically results in increased latency or 502 errors when the load balancer times out, not a direct 503.
- C
The health check settings are configured incorrectly, causing healthy instances to be marked as unhealthy.
Why wrong: Misconfigured health checks would show the targets as unhealthy in the console; the scenario states targets are healthy.
- D
The security group for the targets does not allow traffic from the ALB.
Why wrong: A missing security group rule would cause health checks to fail and targets to be marked unhealthy, but the scenario states health checks pass.
Quick Answer
The answer is that the target instances have reached the maximum number of concurrent connections allowed by the application or operating system. This is the most likely cause of ALB 503 errors due to full connection queue because when the target’s connection queue is saturated, the load balancer cannot establish new connections, even though health checks remain passing. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how ALB connection draining and target connection limits differ from capacity or security group issues—a common trap is confusing 503 errors (connection queue full) with 502 errors (bad gateway or timeout). Remember that healthy targets with 503s point to the target’s own connection ceiling, not the load balancer’s. Memory tip: “503 = Queue is full, 502 = Gateway issue for you.”
SOA-C02 Monitoring, Logging, and Remediation Practice Question
This SOA-C02 practice question tests your understanding of monitoring, logging, and remediation. 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 SysOps administrator is troubleshooting an issue where an Application Load Balancer (ALB) is returning HTTP 503 errors to clients. The target group is healthy, and the instances are passing health checks. 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 target instances have reached the maximum number of concurrent connections allowed by the application or operating system.
Option C is correct because HTTP 503 errors from an ALB typically indicate the load balancer cannot establish a connection to the target due to the target's connection queue being full. Option A is wrong because insufficient capacity usually causes 502 or timeout errors, not 503. Option B is wrong because misconfigured health checks would show unhealthy targets. Option D is wrong because a missing security group rule would cause 502 or timeout.
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 target instances have reached the maximum number of concurrent connections allowed by the application or operating system.
Why this is correct
When the application's connection backlog is full, the ALB receives a 'connection refused' or timeout, resulting in a 503.
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.
- ✗
The target instances do not have enough capacity to handle the request volume.
Why it's wrong here
Insufficient capacity typically results in increased latency or 502 errors when the load balancer times out, not a direct 503.
- ✗
The health check settings are configured incorrectly, causing healthy instances to be marked as unhealthy.
Why it's wrong here
Misconfigured health checks would show the targets as unhealthy in the console; the scenario states targets are healthy.
- ✗
The security group for the targets does not allow traffic from the ALB.
Why it's wrong here
A missing security group rule would cause health checks to fail and targets to be marked unhealthy, but the scenario states health checks pass.
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.
Trap categories for this question
Command / output trap
Misconfigured health checks would show the targets as unhealthy in the console; the scenario states targets are healthy.
Scenario analysis trap
Misconfigured health checks would show the targets as unhealthy in the console; the scenario states targets are healthy.
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 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.
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.
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Monitoring, Logging, and Remediation — This question tests Monitoring, Logging, and Remediation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The target instances have reached the maximum number of concurrent connections allowed by the application or operating system. — Option C is correct because HTTP 503 errors from an ALB typically indicate the load balancer cannot establish a connection to the target due to the target's connection queue being full. Option A is wrong because insufficient capacity usually causes 502 or timeout errors, not 503. Option B is wrong because misconfigured health checks would show unhealthy targets. Option D is wrong because a missing security group rule would cause 502 or timeout.
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.
About these practice questions
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Last reviewed: Jun 20, 2026
This SOA-C02 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 SOA-C02 exam.
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