The answer is the missing permission is kms:CreateGrant. This is required because when RDS creates a snapshot of an encrypted DB instance, it must delegate access to the customer-managed KMS key on your behalf, and a grant is the mechanism that allows RDS to use that key without exposing the key material. Without kms:CreateGrant, the snapshot creation fails even if kms:Decrypt and kms:GenerateDataKey are present, as those only cover data encryption operations, not the delegation of key usage. On the AWS Certified Database Specialty DBS-C01 exam, this is a classic trap: candidates often assume decrypt or encrypt permissions are sufficient, but the key insight is that RDS acts as a proxy requiring a grant to create the snapshot. A helpful memory tip is “Grant for the grant” — whenever a service needs to use your KMS key on your behalf for a new operation like snapshot creation, think of the CreateGrant action first.
DBS-C01 Database Security Practice Question
This DBS-C01 practice question tests your understanding of database security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 IAM policy is attached to a role used by an application to access an Amazon RDS for MySQL DB instance. The DB instance is encrypted with a customer-managed KMS key. The application is unable to create a snapshot of the encrypted DB instance. 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
✓
kms:CreateGrant
Option D is correct. To create a snapshot of an encrypted RDS instance, the IAM role needs permission to the KMS key for the kms:CreateGrant action. The policy allows kms:Decrypt and kms:GenerateDataKey but not kms:CreateGrant, which is required for RDS to use the KMS key on behalf of the user when creating a snapshot. Options A, B, and C are not required for snapshot creation.
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.
✗
kms:ReEncrypt
Why it's wrong here
kms:ReEncrypt is not required for snapshot creation.
✗
kms:DescribeKey
Why it's wrong here
kms:DescribeKey is not required for snapshot creation.
✓
kms:CreateGrant
Why this is correct
RDS needs kms:CreateGrant to authorize RDS to use the KMS key for snapshot operations.
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.
✗
kms:Encrypt
Why it's wrong here
kms:Encrypt is not needed for snapshot creation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 DBS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Database Security — This question tests Database Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: kms:CreateGrant — Option D is correct. To create a snapshot of an encrypted RDS instance, the IAM role needs permission to the KMS key for the kms:CreateGrant action. The policy allows kms:Decrypt and kms:GenerateDataKey but not kms:CreateGrant, which is required for RDS to use the KMS key on behalf of the user when creating a snapshot. Options A, B, and C are not required for snapshot creation.
What should I do if I get this DBS-C01 question wrong?
Identify which DBS-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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