This DOP-C02 practice question tests your understanding of security and compliance. 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 company is migrating to AWS and has a requirement to encrypt all data at rest and in transit. They are using AWS KMS with Customer Master Keys (CMKs) for encryption. The DevOps engineer has set up an S3 bucket with default encryption using SSE-KMS. The bucket policy allows access only to a specific IAM role. The engineer also enabled S3 bucket versioning and MFA Delete. However, when the engineer tries to download an object using the AWS CLI with the IAM role, the command fails with 'AccessDenied'. The IAM role has the following permissions: s3:GetObject, s3:ListBucket, kms:Decrypt, kms:DescribeKey. What is the most likely missing permission?
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
✓
The KMS key policy does not grant the IAM role permission to decrypt using the key.
To download an object encrypted with SSE-KMS, the IAM role must have kms:GenerateDataKey (if uploading) and kms:Decrypt (if downloading). However, for GetObject, KMS requires kms:Decrypt. But there is also a need for kms:Encrypt? Actually, reading encrypted data requires only kms:Decrypt. However, the error might be due to the IAM role not having kms:GenerateDataKey? No, that is for writing. The bucket policy might require kms:Encrypt? Wait. The common missing permission is kms:ReEncrypt? No. Actually, for downloading, KMS permission needed is kms:Decrypt. But the error persists. Could be kms:DescribeKey is not needed. But the most likely is that the KMS key policy does not grant the IAM role permissions. The key policy must allow the IAM role to use the key. The question says the IAM role has kms:Decrypt, but the key policy might not grant it. Option A is correct. Option B is for writing. Option C is not needed. Option D is for management.
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.
✗
The IAM role is missing kms:GenerateDataKey permission.
Why it's wrong here
GenerateDataKey is for uploading, not downloading.
✗
The IAM role is missing kms:Encrypt permission.
Why it's wrong here
Encrypt is not needed for download.
✗
The IAM role is missing kms:CreateGrant permission.
Why it's wrong here
CreateGrant is used for granting access to the key.
✓
The KMS key policy does not grant the IAM role permission to decrypt using the key.
Why this is correct
KMS key policies must explicitly grant access to IAM roles.
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.
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 DOP-C02 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.
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The KMS key policy does not grant the IAM role permission to decrypt using the key. — To download an object encrypted with SSE-KMS, the IAM role must have kms:GenerateDataKey (if uploading) and kms:Decrypt (if downloading). However, for GetObject, KMS requires kms:Decrypt. But there is also a need for kms:Encrypt? Actually, reading encrypted data requires only kms:Decrypt. However, the error might be due to the IAM role not having kms:GenerateDataKey? No, that is for writing. The bucket policy might require kms:Encrypt? Wait. The common missing permission is kms:ReEncrypt? No. Actually, for downloading, KMS permission needed is kms:Decrypt. But the error persists. Could be kms:DescribeKey is not needed. But the most likely is that the KMS key policy does not grant the IAM role permissions. The key policy must allow the IAM role to use the key. The question says the IAM role has kms:Decrypt, but the key policy might not grant it. Option A is correct. Option B is for writing. Option C is not needed. Option D is for management.
What should I do if I get this DOP-C02 question wrong?
Identify which DOP-C02 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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