DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. 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.
An administrator is setting up an AWS DMS replication instance and attaches the IAM policy shown in the exhibit. The administrator receives an error that the replication instance cannot be created. Which missing permission is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ec2:DescribeSecurityGroups
When creating a DMS replication instance, AWS DMS needs to create and manage network interfaces in the customer's VPC. The `ec2:DescribeSecurityGroups` permission is required for DMS to validate and describe the security groups specified during replication instance creation. Without this permission, the service cannot verify the security group IDs, leading to a creation failure.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
ec2:DescribeVpcPeeringConnections
Why it's wrong here
DescribeVpcs is already present; peering connections are not required.
✓
ec2:DescribeSecurityGroups
Why this is correct
DMS needs to describe security groups to attach to the replication instance.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
ec2:CreateNetworkInterfacePermission
Why it's wrong here
The policy already includes ec2:CreateNetworkInterface, which is sufficient.
✗
dms:CreateReplicationInstance
Why it's wrong here
While this action is needed, the error is likely due to missing EC2 permissions to describe security groups.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often focus on the DMS-specific action (`dms:CreateReplicationInstance`) or assume network interface creation is the missing permission, overlooking that DMS requires read-only EC2 describe permissions to validate the VPC resources before creation.
Detailed technical explanation
How to think about this question
Under the hood, DMS uses the `AWSDMS` service-linked role to create elastic network interfaces (ENIs) in the VPC subnet. The user-attached IAM policy must include `ec2:DescribeSecurityGroups` and `ec2:DescribeSubnets` to allow DMS to validate the network configuration before provisioning. A real-world scenario is when a policy grants `ec2:CreateNetworkInterface` but omits `ec2:DescribeSecurityGroups`, causing a silent failure during replication instance creation.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ec2:DescribeSecurityGroups — When creating a DMS replication instance, AWS DMS needs to create and manage network interfaces in the customer's VPC. The `ec2:DescribeSecurityGroups` permission is required for DMS to validate and describe the security groups specified during replication instance creation. Without this permission, the service cannot verify the security group IDs, leading to a creation failure.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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