Quick Answer
The answer is that the EC2 instance profile for the EMR cluster is missing the kms:Decrypt permission, even though the IAM role for the cluster includes it. This is because EMR uses an instance profile—a separate IAM role assigned to the underlying EC2 instances—to make the actual API calls to S3 and KMS. When EMR reads data encrypted with SSE-KMS, the instance profile must have explicit kms:Decrypt permission to decrypt the object; without it, S3 returns a 403 Access Denied error despite the cluster role having the policy. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of the separation between the EMR service role and the EC2 instance profile—a common trap where candidates assume the cluster’s IAM role is sufficient. Remember: the instance profile is the one that touches KMS, not the cluster role. Memory tip: “Instance profile decrypts; cluster role just directs.”
This DEA-C01 practice question tests your understanding of data security and governance. 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 uses Amazon EMR to process data stored in S3 with server-side encryption using AWS KMS. The EMR cluster fails with a "403 Access Denied" error when reading data from S3. The IAM role for the EMR cluster has s3:GetObject and kms:Decrypt permissions. What is the most likely issue?
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.
The EC2 instance profile does not have kms:Decrypt permission
The instance profile must have KMS decrypt permission.
The S3 bucket policy denies access to the EMR cluster's IAM role
Why wrong: Bucket policy likely allows.
The EMRFS consistent view is not enabled
Why wrong: Consistent view is for eventual consistency, not encryption.
The EMR cluster is using an incorrect KMS key ID
Why wrong: The key ID is typically specified correctly.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The EC2 instance profile does not have kms:Decrypt permission
Option D is correct. EMR EC2 instance profile must have the necessary permissions. Often the instance profile is missing kms:Decrypt. Option A is wrong because SSE-KMS requires kms:Decrypt. Option B is wrong because S3 bucket policy might allow. Option C is wrong because EMRFS consistent view is not related.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The EC2 instance profile does not have kms:Decrypt permission
Why this is correct
The instance profile must have KMS decrypt permission.
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.
The S3 bucket policy denies access to the EMR cluster's IAM role
Why it's wrong here
Bucket policy likely allows.
The EMRFS consistent view is not enabled
Why it's wrong here
Consistent view is for eventual consistency, not encryption.
The EMR cluster is using an incorrect KMS key ID
Why it's wrong here
The key ID is typically specified correctly.
Common exam traps
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
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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.
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FAQ
Data Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
The correct answer is: The EC2 instance profile does not have kms:Decrypt permission — Option D is correct. EMR EC2 instance profile must have the necessary permissions. Often the instance profile is missing kms:Decrypt. Option A is wrong because SSE-KMS requires kms:Decrypt. Option B is wrong because S3 bucket policy might allow. Option C is wrong because EMRFS consistent view is not related.
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.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
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