- A
The EC2 instances are failing health checks.
Why wrong: Health check failures would cause 503 but not necessarily at high request rates.
- B
The SSL certificate is expiring.
Why wrong: SSL expiration would cause handshake failures, not 503.
- C
The ALB is exceeding its connection limit.
ALB has a default limit that can be increased via a limit increase request.
- D
The target group's connection draining is too short.
Why wrong: Connection draining would cause errors during instance deregistration, not at high rates.
Question 1,223 of 1,616
ALB 503 Error Connection Limit
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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.
An application uses an Application Load Balancer (ALB) with a target group of EC2 instances. Users report intermittent HTTP 503 errors. The ALB access logs show that the error occurs when the request rate exceeds 10,000 requests per second. 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 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 ALB is exceeding its connection limit.
The correct answer is C. Application Load Balancers have a default limit of 10,000 new connections per second (this can be increased via a limit increase request). When the request rate exceeds this limit, the ALB returns HTTP 503 errors. Option A is incorrect because if EC2 instances were failing health checks, the ALB would route traffic to healthy instances, and the error would not be tied to a specific request rate. Option B is incorrect because an expiring SSL certificate would cause certificate validation errors, not 503 errors. Option D is incorrect because connection draining affects the graceful shutdown of instances and would not cause 503 errors when the request rate exceeds the ALB's limits.
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 EC2 instances are failing health checks.
Why it's wrong here
Health check failures would cause 503 but not necessarily at high request rates.
- ✗
The SSL certificate is expiring.
Why it's wrong here
SSL expiration would cause handshake failures, not 503.
- ✓
The ALB is exceeding its connection limit.
Why this is correct
ALB has a default limit that can be increased via a limit increase request.
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 group's connection draining is too short.
Why it's wrong here
Connection draining would cause errors during instance deregistration, not at high rates.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which DVA-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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Troubleshooting and Optimization — study guide chapter
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ALB is exceeding its connection limit. — The correct answer is C. Application Load Balancers have a default limit of 10,000 new connections per second (this can be increased via a limit increase request). When the request rate exceeds this limit, the ALB returns HTTP 503 errors. Option A is incorrect because if EC2 instances were failing health checks, the ALB would route traffic to healthy instances, and the error would not be tied to a specific request rate. Option B is incorrect because an expiring SSL certificate would cause certificate validation errors, not 503 errors. Option D is incorrect because connection draining affects the graceful shutdown of instances and would not cause 503 errors when the request rate exceeds the ALB's limits.
What should I do if I get this DVA-C02 question wrong?
Identify which DVA-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
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 →
Same concept, more angles
2 more ways this is tested on DVA-C02
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 web application running on EC2 instances behind an Application Load Balancer (ALB) is experiencing intermittent 503 errors. The ALB target group health checks are succeeding. Which step should the developer take FIRST to diagnose the issue?
medium- A.Increase the number of EC2 instances in the target group.
- ✓ B.Examine the ALB access logs for 503 responses.
- C.Check the Route 53 record for the ALB.
- D.Verify that the EC2 instances are in a running state.
Why B: The correct first step is to examine the ALB access logs for 503 responses. Since health checks are succeeding, the EC2 instances are considered healthy by the target group, but the ALB itself may be returning 503 errors due to issues like request rate limits, connection limits, or backend response timeouts. Access logs provide detailed HTTP response codes and timestamps, allowing you to identify the pattern and cause of the 503 errors without making assumptions about instance count or state.
Variation 2. An application running on EC2 instances behind an Application Load Balancer (ALB) occasionally returns HTTP 503 errors. The instances are in an Auto Scaling group. Which action should be taken to resolve this issue?
hard- A.Enable cross-zone load balancing on the ALB.
- ✓ B.Review the ALB access logs to identify the target response codes.
- C.Increase the ALB idle timeout setting.
- D.Increase the size of the EC2 instances.
Why B: HTTP 503 errors from an ALB indicate that the targets (EC2 instances) are not responding successfully. Reviewing ALB access logs reveals the specific target response codes (e.g., 503 from the target itself or connection timeouts), which helps pinpoint whether the issue is due to overloaded instances, application errors, or health check failures. This diagnostic step is essential before making any configuration changes.
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Last reviewed: Jun 20, 2026
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