- A
The Lambda function's execution role does not have permission to invoke the function.
Why wrong: Incorrect. The error occurs during S3 write, not during invocation. Invocation was successful if the function started.
- B
The Lambda function's IAM role is missing the kms:Encrypt permission on the CMK.
Why wrong: Incorrect. For SSE-KMS writes, only kms:GenerateDataKey is required; kms:Encrypt is not used by the caller. The role already has kms:GenerateDataKey and kms:Decrypt, so KMS permissions are sufficient.
- C
The S3 bucket policy denies s3:PutObject from the Lambda function.
Correct. Although the stem says the bucket policy allows, an explicit deny statement in the policy would override the allow and cause an access denied error. This is the most likely cause given the error.
- D
The Kinesis data stream is not encrypted, causing the Lambda function to fail.
Why wrong: Incorrect. Stream encryption does not affect S3 write operations.
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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The S3 bucket policy denies s3:PutObject from the Lambda function.
The most likely cause is that the S3 bucket policy denies s3:PutObject from the Lambda function's IAM role. Even though the stem states the policy allows, there could be an explicit deny statement that overrides, resulting in an 'Access Denied' error. The Lambda function's IAM role has the necessary KMS permissions (kms:GenerateDataKey and kms:Decrypt) for SSE-KMS writes, so missing kms:Encrypt is not the issue. Option A is incorrect because invocation permissions are unrelated. Option B is incorrect because kms:Encrypt is not required for SSE-KMS writes. Option D is incorrect because Kinesis stream encryption is unrelated.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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
Incorrect. The error occurs during S3 write, not during invocation. Invocation was successful if the function started.
- ✗
The Lambda function's IAM role is missing the kms:Encrypt permission on the CMK.
Why it's wrong here
Incorrect. For SSE-KMS writes, only kms:GenerateDataKey is required; kms:Encrypt is not used by the caller. The role already has kms:GenerateDataKey and kms:Decrypt, so KMS permissions are sufficient.
- ✓
The S3 bucket policy denies s3:PutObject from the Lambda function.
Why this is correct
Correct. Although the stem says the bucket policy allows, an explicit deny statement in the policy would override the allow and cause an access denied error. This is the most likely cause given the error.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
- ✗
The Kinesis data stream is not encrypted, causing the Lambda function to fail.
Why it's wrong here
Incorrect. Stream encryption does not affect S3 write operations.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DEA-C01 ACL questions on filtering logic and placement.
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Security and Governance — This question tests Data Security and Governance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The S3 bucket policy denies s3:PutObject from the Lambda function. — The most likely cause is that the S3 bucket policy denies s3:PutObject from the Lambda function's IAM role. Even though the stem states the policy allows, there could be an explicit deny statement that overrides, resulting in an 'Access Denied' error. The Lambda function's IAM role has the necessary KMS permissions (kms:GenerateDataKey and kms:Decrypt) for SSE-KMS writes, so missing kms:Encrypt is not the issue. Option A is incorrect because invocation permissions are unrelated. Option B is incorrect because kms:Encrypt is not required for SSE-KMS writes. Option D is incorrect because Kinesis stream encryption is unrelated.
What should I do if I get this DEA-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DEA-C01 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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Last reviewed: Jun 20, 2026
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