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Troubleshooting and Optimization →mediumMultiple ChoiceObjective-mapped

DVA-C02 Troubleshooting and Optimization Practice Question

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.

A company is using AWS Elastic Beanstalk for a Node.js application. The environment's health is 'Severe' and the logs show 'ELB health check target http://:80/ is not responding'. 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.

A
The application is not deployed to the EC2 instances.
Why wrong: If not deployed, the health check would fail, but the error message points to the target path and port.
B
The application is listening on a different port than the health check expects.
The health check URL shows port 80, but the application may be configured to listen on a custom port, causing the health check to fail.
C
The security group for the EC2 instances is blocking traffic on port 80.
Why wrong: The health check is made by the load balancer, and if the security group blocks it, the health check would fail, but the error message shows the health check target is not responding, indicating the application is not listening.
D
The load balancer is not configured to listen on port 80.
Why wrong: The load balancer listener is separate from the health check target; the health check is failing because the application is not responding on that path.

Full breakdown with real-world context →

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 application is listening on a different port than the health check expects.

Option B is correct. The health check target 'http://:80/' indicates that the load balancer is trying to connect to port 80 on the EC2 instances, but the application is not listening on that port. This is a common misconfiguration when the application uses a custom port. Option A is incorrect because if the application were not deployed, the error would typically be a 503 or 'no healthy instances' rather than a specific health check target not responding. Option C is incorrect because a security group blocking port 80 would result in a connection timeout, not a health check failure. Option D is incorrect because the load balancer is configured to listen on port 80, as shown by the health check target, so the issue is on the instance side.

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 application is not deployed to the EC2 instances.
Why it's wrong here
If not deployed, the health check would fail, but the error message points to the target path and port.
✓
The application is listening on a different port than the health check expects.
Why this is correct
The health check URL shows port 80, but the application may be configured to listen on a custom port, causing the health check to fail.
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 security group for the EC2 instances is blocking traffic on port 80.
Why it's wrong here
The health check is made by the load balancer, and if the security group blocks it, the health check would fail, but the error message shows the health check target is not responding, indicating the application is not listening.
✗
The load balancer is not configured to listen on port 80.
Why it's wrong here
The load balancer listener is separate from the health check target; the health check is failing because the application is not responding on that path.

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
The health check is made by the load balancer, and if the security group blocks it, the health check would fail, but the error message shows the health check target is not responding, indicating the application is not listening.

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 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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Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

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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 application is listening on a different port than the health check expects. — Option B is correct. The health check target 'http://:80/' indicates that the load balancer is trying to connect to port 80 on the EC2 instances, but the application is not listening on that port. This is a common misconfiguration when the application uses a custom port. Option A is incorrect because if the application were not deployed, the error would typically be a 503 or 'no healthy instances' rather than a specific health check target not responding. Option C is incorrect because a security group blocking port 80 would result in a connection timeout, not a health check failure. Option D is incorrect because the load balancer is configured to listen on port 80, as shown by the health check target, so the issue is on the instance side.

What should I do if I get this DVA-C02 question wrong?

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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