The answer is DB subnet groups and security groups. Security groups act as a virtual firewall, controlling inbound and outbound traffic to your RDS instance at the network interface level, while DB subnet groups define which subnets within your VPC the instance can be deployed into, indirectly controlling network access by restricting placement to specific private subnets. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your ability to distinguish between network-level controls and other configuration tools—a common trap is confusing IAM policies or parameter groups with network access. Remember that security groups filter traffic, subnet groups dictate placement, and neither IAM nor parameter groups handle network rules. A helpful memory tip: “Security groups guard the door, subnet groups choose the room.”
DBS-C01 Database Security Practice Question
This DBS-C01 practice question tests your understanding of database 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.
Which TWO of the following are valid methods to control network access to an Amazon RDS DB instance? (Select TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VPC security groups
Options B and D are correct. Security groups control inbound and outbound traffic to RDS instances. DB subnet groups define which subnets the DB instance can be placed in, but they indirectly control network access. Option A (IAM policies) control API-level permissions, not network access. Option C (DB parameter groups) control database engine settings. Option E (AWS WAF) is for web application firewalls, not network-level access to RDS.
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.
✓
VPC security groups
Why this is correct
Security groups act as a virtual firewall for your DB instance to control inbound and outbound traffic.
AWS WAF is a web application firewall, not used for network access to RDS.
✗
IAM policies
Why it's wrong here
IAM policies control permissions to perform actions on RDS resources, not network access.
✗
DB parameter groups
Why it's wrong here
Parameter groups manage database engine configuration, not network access.
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 DBS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Database Security — This question tests Database Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: VPC security groups — Options B and D are correct. Security groups control inbound and outbound traffic to RDS instances. DB subnet groups define which subnets the DB instance can be placed in, but they indirectly control network access. Option A (IAM policies) control API-level permissions, not network access. Option C (DB parameter groups) control database engine settings. Option E (AWS WAF) is for web application firewalls, not network-level access to RDS.
What should I do if I get this DBS-C01 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 DBS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company wants to restrict access to an Amazon RDS for MySQL DB instance so that only applications running in a specific VPC can connect. Which solution should be implemented?
easy
A.Use an IAM policy to restrict database connections based on source IP.
✓ B.Configure the DB instance's security group to allow inbound traffic only from the application's security group.
C.Configure the subnet's network ACL to allow inbound traffic only from the application's IP range.
D.Attach a security group to the subnet that allows inbound traffic from the application's VPC.
Why B: Option A is correct because a VPC security group controls inbound traffic at the instance level. Option B is wrong because network ACLs are for subnets, not individual instances. Option C is wrong because IAM policies control API access, not network connectivity. Option D is wrong because security groups are not attached to subnets.
Last reviewed: Jun 20, 2026
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This DBS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DBS-C01 exam.
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