The correct answer is to add a statement to the KMS key policy allowing the IAM user to call kms:Decrypt. This is because a KMS key policy acts as the primary resource-based policy for a customer master key, explicitly defining who can use the key and under what conditions. When you grant kms:Decrypt via KMS key policy, you are directly controlling access at the key level, which is essential for cross-account scenarios or when you need to ensure the key itself permits the action before any IAM policy can take effect. On the AWS Certified Data Engineer Associate DEA-C01 exam, this concept tests your understanding of the layered permission model: while IAM policies can grant KMS permissions, the key policy must explicitly allow the IAM entity’s account, or the IAM policy alone will be ineffective. A common trap is assuming an IAM policy alone suffices for a specific key, but the key policy is the gatekeeper. Memory tip: think of the key policy as the bouncer at the door—no matter what your IAM badge says, the bouncer must let you in first.
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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.
A data engineer needs to grant an IAM user read-only access to a specific KMS key for decrypting S3 objects. Which policy element should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a statement to the KMS key policy allowing the IAM user to call kms:Decrypt
A KMS key policy can grant IAM users permissions directly. Option B is wrong because IAM policies can also grant KMS permissions, but the key policy must allow the IAM policy. Option C is wrong because SCPs are for Organizations. Option D is wrong because bucket policies do not grant KMS permissions. Option A is correct, though both A and B are possible; typically key policy is used for cross-account or specific grants.
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.
✗
Attach an IAM policy to the user allowing kms:Decrypt
Why it's wrong here
This works only if the key policy enables IAM policies, which is default, but key policy is more direct.
✓
Add a statement to the KMS key policy allowing the IAM user to call kms:Decrypt
Why this is correct
Key policies directly grant access to the key.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a bucket policy that grants kms:Decrypt
Why it's wrong here
Bucket policies cannot grant KMS actions.
✗
Use an SCP in AWS Organizations to allow kms:Decrypt
Why it's wrong here
SCPs are for account boundaries, not individual users.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which DEA-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.
Data Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a statement to the KMS key policy allowing the IAM user to call kms:Decrypt — A KMS key policy can grant IAM users permissions directly. Option B is wrong because IAM policies can also grant KMS permissions, but the key policy must allow the IAM policy. Option C is wrong because SCPs are for Organizations. Option D is wrong because bucket policies do not grant KMS permissions. Option A is correct, though both A and B are possible; typically key policy is used for cross-account or specific grants.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This DEA-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 DEA-C01 exam.
Question Discussion
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