The correct answer is to place the RDS instances in private subnets and apply a security group to control inbound traffic. Placing the database in a private subnet ensures it has no direct internet access, which is the foundational step for a secure RDS private subnet security group configuration. The security group then acts as a virtual firewall, explicitly allowing only necessary traffic—such as from an application tier—while blocking all other inbound connections. On the AWS Certified Developer Associate DVA-C02 exam, this question tests your understanding of layered network security within a VPC; a common trap is confusing stateless network ACLs with stateful security groups, or assuming IAM roles handle direct database connections. Remember, security groups are stateful and are the primary mechanism for RDS access control, while NACLs are a secondary, stateless layer. Memory tip: "Private subnet plus security group equals database fortress."
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 has a VPC with public and private subnets. The private subnets contain Amazon RDS databases. Which TWO actions are required to secure the database instances?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure security groups to allow only necessary traffic from application servers.
Option A is correct because placing RDS in a private subnet prevents direct internet access. Option C is correct because security groups control inbound traffic to the database. Option B is wrong because public subnets would expose the database. Option D is wrong because NACLs are stateless and not the primary security mechanism for RDS. Option E is wrong because IAM roles are not used to connect to RDS (user/password or IAM database authentication).
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.
✓
Configure security groups to allow only necessary traffic from application servers.
Why this is correct
Security groups act as a virtual firewall for the database.
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 DVA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Security — This question tests Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure security groups to allow only necessary traffic from application servers. — Option A is correct because placing RDS in a private subnet prevents direct internet access. Option C is correct because security groups control inbound traffic to the database. Option B is wrong because public subnets would expose the database. Option D is wrong because NACLs are stateless and not the primary security mechanism for RDS. Option E is wrong because IAM roles are not used to connect to RDS (user/password or IAM database authentication).
What should I do if I get this DVA-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 DVA-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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Question Discussion
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