DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. 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 is deploying a new Amazon RDS for MariaDB instance. The database must be accessible from a specific set of EC2 instances in a VPC. How should the company configure security to allow access?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a security group for the RDS instance that allows inbound traffic from the EC2 instances' security group.
Option C is correct because the RDS security group should allow inbound traffic from the EC2 security group. Option A is wrong because NACLs are stateless and less granular. Option B is wrong because RDS does not support EC2 classic security groups. Option D is wrong because IAM roles are for authentication, not network access.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Assign the same security group to both the RDS instance and the EC2 instances.
Why it's wrong here
RDS and EC2 cannot share the same security group; use security group referencing.
✓
Create a security group for the RDS instance that allows inbound traffic from the EC2 instances' security group.
Why this is correct
Security group referencing is the best practice for allowing access from EC2.
Related concept
Standard ACLs match source addresses.
✗
Attach an IAM role to the EC2 instances that grants access to the RDS database.
Why it's wrong here
IAM roles are for authentication and authorization, not network access.
✗
Configure a network ACL to allow inbound traffic from the EC2 instance IPs.
Why it's wrong here
NACLs are for subnets, not for controlling access to a specific RDS instance.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
Deployment and Migration — This question tests Deployment and Migration — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Create a security group for the RDS instance that allows inbound traffic from the EC2 instances' security group. — Option C is correct because the RDS security group should allow inbound traffic from the EC2 security group. Option A is wrong because NACLs are stateless and less granular. Option B is wrong because RDS does not support EC2 classic security groups. Option D is wrong because IAM roles are for authentication, not network access.
What should I do if I get this DBS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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