- A
The CodeBuild project's VPC configuration does not include the subnet IDs where the database resides.
Why wrong: CodeBuild requires both VPC ID and subnet IDs.
- B
The security group for the CodeBuild project does not allow outbound traffic to the RDS database.
Why wrong: Outbound rules are typically allow-all; inbound rules on the database side are the issue.
- C
The security group for the RDS database does not allow inbound traffic from the security group assigned to the CodeBuild project.
The database's security group must allow inbound from the CodeBuild security group.
- D
The CodeBuild project does not have a route to the internet via an internet gateway, so it cannot reach the RDS endpoint.
Why wrong: RDS in a private subnet does not require internet access; it can be reached via VPC routing.
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 team uses AWS CodeBuild to run integration tests that require access to an Amazon RDS database. The database is in a private subnet. The CodeBuild project is configured to use a VPC. However, the builds are failing with a timeout connecting to the database. What could be the issue?
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 security group for the RDS database does not allow inbound traffic from the security group assigned to the CodeBuild project.
Option C is correct because the RDS database is in a private subnet and its security group must explicitly allow inbound traffic from the CodeBuild project's security group. Even though CodeBuild is configured with a VPC, the default security group rules deny all inbound traffic; without an inbound rule for the database port (e.g., 3306 for MySQL) from the CodeBuild security group, the connection is blocked, causing a 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 CodeBuild project's VPC configuration does not include the subnet IDs where the database resides.
Why it's wrong here
CodeBuild requires both VPC ID and subnet IDs.
- ✗
The security group for the CodeBuild project does not allow outbound traffic to the RDS database.
Why it's wrong here
Outbound rules are typically allow-all; inbound rules on the database side are the issue.
- ✓
The security group for the RDS database does not allow inbound traffic from the security group assigned to the CodeBuild project.
Why this is correct
The database's security group must allow inbound from the CodeBuild security group.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The CodeBuild project does not have a route to the internet via an internet gateway, so it cannot reach the RDS endpoint.
Why it's wrong here
RDS in a private subnet does not require internet access; it can be reached via VPC routing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the issue is outbound traffic (Option B) or subnet configuration (Option A), but the real problem is the missing inbound rule on the database security group, which is a classic security group misconfiguration in VPC-connected services.
Detailed technical explanation
How to think about this question
Security groups in AWS are stateful firewalls that track connection state; when CodeBuild sends a TCP SYN to the RDS database, the security group for the database must have an inbound rule allowing the traffic, but the response (SYN-ACK) is automatically permitted regardless of outbound rules. In a VPC, CodeBuild uses elastic network interfaces (ENIs) in the specified subnets, and the database's security group must reference the CodeBuild security group (or the CIDR of the subnet) for the specific database port. A common real-world scenario is forgetting to update the inbound rule after changing the CodeBuild project's security group, leading to intermittent timeouts.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
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 RDS database does not allow inbound traffic from the security group assigned to the CodeBuild project. — Option C is correct because the RDS database is in a private subnet and its security group must explicitly allow inbound traffic from the CodeBuild project's security group. Even though CodeBuild is configured with a VPC, the default security group rules deny all inbound traffic; without an inbound rule for the database port (e.g., 3306 for MySQL) from the CodeBuild security group, the connection is blocked, causing a timeout.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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