The correct choice is to configure the security group for the RDS instance to allow inbound traffic from the security group associated with the CodeBuild project. This works because CodeBuild, when configured with a VPC, runs inside that VPC and uses its own security group for outbound traffic; the RDS instance in the private subnet will only accept connections if its inbound security group explicitly permits traffic from the CodeBuild security group. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding that VPC connectivity for CodeBuild is a two-way security group rule, not a networking gateway or endpoint—a common trap is confusing NAT gateways (for internet egress) or VPC endpoints (for AWS API access) with direct database access. Remember the memory tip: "CodeBuild talks to RDS through security group handshake, not through a gateway or endpoint."
DOP-C02 SDLC Automation Practice Question
This DOP-C02 practice question tests your understanding of sdlc automation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 run integration tests as part of a pipeline. The tests require access to an Amazon RDS database. The RDS instance is in a private subnet with no public access. The CodeBuild project is configured with a VPC. Which additional configuration is necessary to ensure the build can connect to the database?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the security group for the RDS instance to allow inbound traffic from the security group associated with the CodeBuild project.
Option C is correct because CodeBuild needs security group rules that allow outbound traffic to the RDS instance and the RDS security group must allow inbound traffic from CodeBuild. Option A is wrong because NATgateway is for internet access, not for database connectivity within VPC. Option B is wrong because VPC endpoints are for AWS services, not for RDS connectivity. Option D is wrong because IAM roles do not control network connectivity.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Add an IAM policy that grants the CodeBuild service role access to the RDS instance.
Why it's wrong here
IAM policies control API permissions, not network connectivity; security groups are required.
✓
Configure the security group for the RDS instance to allow inbound traffic from the security group associated with the CodeBuild project.
Why this is correct
Security group rules must allow traffic between CodeBuild and RDS for connectivity.
VPC endpoints are used to access RDS API operations, not data plane connectivity to the database instance.
✗
Attach a NAT gateway to the private subnet.
Why it's wrong here
NATgateway enables outbound internet access, but the database is within the same VPC, so it's not needed for connectivity.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
SDLC Automation — This question tests SDLC Automation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure the security group for the RDS instance to allow inbound traffic from the security group associated with the CodeBuild project. — Option C is correct because CodeBuild needs security group rules that allow outbound traffic to the RDS instance and the RDS security group must allow inbound traffic from CodeBuild. Option A is wrong because NAT gateway is for internet access, not for database connectivity within VPC. Option B is wrong because VPC endpoints are for AWS services, not for RDS connectivity. Option D is wrong because IAM roles do not control network connectivity.
What should I do if I get this DOP-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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