The answer is that the Lambda function’s IAM role is missing the kms:Encrypt permission on the customer-managed key. When writing to an SSE-KMS encrypted S3 bucket, the Lambda function must have both kms:Encrypt and kms:GenerateDataKey to encrypt the object data during the PutObject operation; having only kms:Decrypt and kms:GenerateDataKey is insufficient because the encryption step itself requires the explicit Encrypt action. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of the full KMS permission chain for S3 SSE-KMS writes—a common trap is assuming that kms:GenerateDataKey alone covers encryption, but AWS requires the separate kms:Encrypt permission for the actual data encryption call. Remember the memory tip: “To write with SSE-KMS, you need Encrypt and GenerateDataKey—Decrypt alone won’t let you lock the box.”
DEA-C01 Data Security and Governance Practice Question
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 data engineering team uses AWS Lambda functions to process streaming data from Amazon Kinesis Data Streams and write the results to an S3 bucket. The S3 bucket is encrypted with SSE-KMS using a customer-managed key (CMK). The Lambda function's IAM role has permissions for kms:Decrypt and kms:GenerateDataKey on the CMK. However, the Lambda function fails with an 'Access Denied' error when writing to S3. The S3 bucket policy allows s3:PutObject from the Lambda function's IAM role. What 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
✓
The Lambda function's IAM role is missing the kms:Encrypt permission on the CMK.
Option A is correct. When writing to S3 with SSE-KMS, the Lambda function needs kms:Encrypt permission to encrypt the data. The role only has kms:Decrypt and kms:GenerateDataKey, missing kms:Encrypt. Option B is wrong because Kinesis encryption is separate. Option C is wrong because the bucket policy allows PutObject. Option D is wrong because Lambda has permissions, but missing kms:Encrypt.
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 Lambda function's execution role does not have permission to invoke the function.
Why it's wrong here
Invocation is not the issue.
✓
The Lambda function's IAM role is missing the kms:Encrypt permission on the CMK.
Why this is correct
Writing encrypted data requires kms:Encrypt.
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 s3:PutObject from the Lambda function.
Why it's wrong here
Bucket policy allows it.
✗
The Kinesis data stream is not encrypted, causing the Lambda function to fail.
Why it's wrong here
Kinesis encryption is independent of S3 write.
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: The Lambda function's IAM role is missing the kms:Encrypt permission on the CMK. — Option A is correct. When writing to S3 with SSE-KMS, the Lambda function needs kms:Encrypt permission to encrypt the data. The role only has kms:Decrypt and kms:GenerateDataKey, missing kms:Encrypt. Option B is wrong because Kinesis encryption is separate. Option C is wrong because the bucket policy allows PutObject. Option D is wrong because Lambda has permissions, but missing kms:Encrypt.
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.
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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