The answer is a misconfigured security group rule on the SonarQube server. While the scenario states the security group allows inbound traffic on port 9000 from the CodeBuild security group, a timeout during the TCP handshake indicates that this rule is either not actually applied, references the wrong security group ID, or is overridden by a deny rule—preventing the three-way handshake from completing. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this tests your understanding that VPC connectivity failures in CodeBuild are almost always network-layer issues, not IAM or certificate problems; a common trap is assuming the stated configuration is correct when the symptom (timeout) directly contradicts it. Remember: a timeout means the packet never reached the target or the reply never returned—always verify the security group’s inbound rule is properly associated with the SonarQube instance and that the CodeBuild project’s VPC configuration includes the correct subnet and security group IDs. Memory tip: “Timeout = Traffic blocked; no timeout = Auth or DNS issue.”
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. 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 uses AWS CodeBuild to compile a Java application. The buildspec.yml includes a 'pre_build' phase that runs SonarQube for static code analysis. The analysis requires access to a private SonarQube server hosted on an EC2 instance in the same VPC. The CodeBuild project is configured with a VPC ID, subnet IDs, and security group IDs. However, the build fails with a timeout when trying to connect to the SonarQube server. The security group for the SonarQube server allows inbound traffic on port 9000 from the CodeBuild security group. What is the MOST likely reason for the failure?
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 security group for the SonarQube server does not allow inbound traffic on port 9000 from the CodeBuild security group.
Option B is correct because the scenario explicitly states that the security group for the SonarQube server allows inbound traffic on port 9000 from the CodeBuild security group, yet the build fails with a timeout. A timeout typically indicates a network connectivity issue, not a certificate or permission problem. The most likely cause is that the security group rule is misconfigured (e.g., using the wrong security group ID, or the rule is not actually applied), preventing the TCP handshake on port 9000 from completing.
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 CodeBuild project is not configured with the correct VPC subnets.
Why it's wrong here
Incorrect subnets would cause a different error, such as failure to launch build container.
✓
The security group for the SonarQube server does not allow inbound traffic on port 9000 from the CodeBuild security group.
Why this is correct
Without inbound rule from CodeBuild's security group, the connection is blocked.
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 SonarQube server is using a self-signed certificate that CodeBuild does not trust.
The CodeBuild project does not have internet access, so it cannot reach the SonarQube server.
Why it's wrong here
The SonarQube server is in the same VPC, so internet access is not required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the security group rule is correctly configured because it is described in the question, but the timeout indicates the rule is either missing, misconfigured, or not applied, making option B the most likely cause despite the description.
Detailed technical explanation
How to think about this question
When CodeBuild runs in a VPC, it uses Elastic Network Interfaces (ENIs) attached to the specified subnets. The security group assigned to CodeBuild must allow outbound traffic (by default, all outbound is allowed), and the SonarQube server's security group must have an inbound rule allowing TCP port 9000 from the CodeBuild security group. A timeout occurs when the TCP SYN packet is sent but no SYN-ACK is received, often because the inbound rule is missing, uses the wrong security group ID, or the rule is not yet propagated. In real-world scenarios, verifying security group rules with tools like `telnet` or `nc` from a similar instance can isolate the issue.
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.
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
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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
SDLC Automation — This question tests SDLC Automation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The security group for the SonarQube server does not allow inbound traffic on port 9000 from the CodeBuild security group. — Option B is correct because the scenario explicitly states that the security group for the SonarQube server allows inbound traffic on port 9000 from the CodeBuild security group, yet the build fails with a timeout. A timeout typically indicates a network connectivity issue, not a certificate or permission problem. The most likely cause is that the security group rule is misconfigured (e.g., using the wrong security group ID, or the rule is not actually applied), preventing the TCP handshake on port 9000 from completing.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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