Controlling Network Access to RDS
Which TWO of the following are valid methods to control network access to an Amazon RDS DB instance? (Select TWO.)
Quick Answer
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.”
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
✓
VPC security groups
A and B are correct. VPC security groups (A) act as a virtual firewall to control inbound and outbound traffic to the RDS instance at the network level. DB subnet groups (B) determine which subnets the RDS instance can be deployed in, effectively controlling network access by restricting the IP ranges that can reach the instance. AWS WAF (C) is a web application firewall for HTTP/HTTPS traffic, not for network-level RDS access. IAM policies (D) control API-level permissions, not network traffic. DB parameter groups (E) manage database engine configuration settings and do not affect network access.
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.
- ✓
DB subnet groups
Why this is correct
Subnet groups define which subnets the DB instance can be placed in, thereby controlling network isolation.
- ✗
AWS WAF
Why it's wrong here
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.
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Same concept, more angles
1 more way this is tested on DBS-C01
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: Security groups act as a virtual firewall for the DB instance, and by allowing inbound traffic only from the application's security group, access is restricted to resources in that VPC. Option A is incorrect because IAM policies control API-level permissions, not network-level access. Option C is incorrect because network ACLs are stateless and apply at the subnet level, not at the instance level. Option D is incorrect because security groups are not attached to subnets; they are attached to network interfaces.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.