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Database Security →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is to create a KMS key with a key policy that includes the condition key `kms:ViaService` set to `dynamodb.amazonaws.com`. This condition explicitly restricts the key’s usage to DynamoDB, ensuring that no other AWS service—such as S3 or EBS—can decrypt data protected by this key, even if an IAM principal has broad permissions. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding that KMS key policies are the authoritative access control for a CMK, and that service-specific conditions are the only way to enforce a service-level restriction. A common trap is assuming an SCP or IAM policy alone can block key usage, but those policies cannot override a key policy that grants access to other services. Memory tip: think of `kms:ViaService` as a “bouncer” that only lets DynamoDB through the door—no other service gets past it.

DBS-C01 Database Security Practice Question

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 financial company uses Amazon DynamoDB to store customer transaction data. The compliance team requires that all data be encrypted at rest using a customer-managed AWS KMS key. Additionally, they need to ensure that the key is used only for DynamoDB and no other AWS service. How can the company meet these requirements?

Question 1hardmultiple choice

Full question →

A
Use a KMS key with no key policy, and rely on IAM policies to restrict access to only DynamoDB.
Why wrong: Without a key policy, no one can use the key; also, IAM alone cannot restrict key usage if the key policy allows it.
B
Use an AWS Organizations service control policy (SCP) to deny all AWS services except DynamoDB from using the KMS key.
Why wrong: SCPs cannot restrict KMS key usage; key policies are required.
C
Create a KMS key with a key policy that includes a condition such as "kms:ViaService": "dynamodb.amazonaws.com" to restrict usage to DynamoDB.
This condition ensures the key can only be used through DynamoDB, preventing other services.
D
Create a KMS key with a key policy that allows DynamoDB to use the key, and attach an IAM policy to deny all other services.
Why wrong: IAM policies cannot override a key policy that grants access to other services.

Full breakdown with real-world context →

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

✓

Create a KMS key with a key policy that includes a condition such as "kms:ViaService": "dynamodb.amazonaws.com" to restrict usage to DynamoDB.

Option D is correct because a KMS key policy with a condition that restricts usage to DynamoDB and prevents other services is the proper way. Option A is wrong because SCPs do not control KMS key permissions. Option B is wrong because IAM policies alone cannot restrict the key usage; the key policy must also enforce it. Option C is wrong because you cannot prevent other services from using the key via IAM if the key policy allows them.

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.

✗
Use a KMS key with no key policy, and rely on IAM policies to restrict access to only DynamoDB.
Why it's wrong here
Without a key policy, no one can use the key; also, IAM alone cannot restrict key usage if the key policy allows it.
✗
Use an AWS Organizations service control policy (SCP) to deny all AWS services except DynamoDB from using the KMS key.
Why it's wrong here
SCPs cannot restrict KMS key usage; key policies are required.
✓
Create a KMS key with a key policy that includes a condition such as "kms:ViaService": "dynamodb.amazonaws.com" to restrict usage to DynamoDB.
Why this is correct
This condition ensures the key can only be used through DynamoDB, preventing other services.
Related concept
Standard ACLs match source addresses.
✗
Create a KMS key with a key policy that allows DynamoDB to use the key, and attach an IAM policy to deny all other services.
Why it's wrong here
IAM policies cannot override a key policy that grants access to other services.

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.

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FAQ

Questions learners often ask

What does this DBS-C01 question test?

Database Security — This question tests Database Security — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: Create a KMS key with a key policy that includes a condition such as "kms:ViaService": "dynamodb.amazonaws.com" to restrict usage to DynamoDB. — Option D is correct because a KMS key policy with a condition that restricts usage to DynamoDB and prevents other services is the proper way. Option A is wrong because SCPs do not control KMS key permissions. Option B is wrong because IAM policies alone cannot restrict the key usage; the key policy must also enforce it. Option C is wrong because you cannot prevent other services from using the key via IAM if the key policy allows them.

What should I do if I get this DBS-C01 question wrong?

What is the key concept behind this question?

Standard ACLs match source addresses.

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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.