This DBS-C01 practice question tests your understanding of database security. 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 is deploying a new Amazon RDS for MySQL database in a VPC. The database must be accessible only from an application server running in the same VPC. The security team also wants to ensure that the database is not accessible from the internet. Which TWO configurations are required? (Choose TWO.)
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 to allow inbound traffic only from the application server's security group.
Options B and D are correct. Option B: Making the DB instance not publicly accessible ensures it cannot be reached from the internet. Option D: Configuring the security group to allow inbound traffic only from the application server's security group limits access. Option A is wrong because a public subnet does not prevent internet access; it enables it. Option C is wrong because a network ACL is stateless and less specific than security groups. Option E is wrong because the parameter group does not control network access.
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.
✗
Place the DB instance in a public subnet.
Why it's wrong here
A public subnet has a route to the internet gateway, which would allow internet access.
✗
Modify the DB parameter group to restrict network access.
Why it's wrong here
Parameter groups do not control network access.
✓
Configure the security group to allow inbound traffic only from the application server's security group.
Why this is correct
This restricts access to the specific application server.
Configure a network ACL to deny inbound traffic from 0.0.0.0/0.
Why it's wrong here
Network ACLs are stateless and less precise; security groups are preferred for this requirement.
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: Configure the security group to allow inbound traffic only from the application server's security group. — Options B and D are correct. Option B: Making the DB instance not publicly accessible ensures it cannot be reached from the internet. Option D: Configuring the security group to allow inbound traffic only from the application server's security group limits access. Option A is wrong because a public subnet does not prevent internet access; it enables it. Option C is wrong because a network ACL is stateless and less specific than security groups. Option E is wrong because the parameter group does not control network access.
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.
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Question Discussion
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