The answer is that the Glue job fails writing to S3 due to missing encryption headers in the write request. This is because the S3 bucket policy explicitly denies access to any principal that does not use server-side encryption, so when the Glue job attempts to write objects without including the required encryption header—such as `x-amz-server-side-encryption: aws:kms`—the policy condition is triggered, resulting in an access denied error. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how S3 bucket policy conditions interact with AWS Glue ETL jobs, particularly the need to match encryption settings between the job configuration and the bucket policy. A common trap is assuming the IAM role alone is sufficient, but the bucket policy’s explicit deny overrides any allow. Remember the memory tip: “No header, no entry”—if the Glue job omits the encryption header, the bucket policy slams the door shut.
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 engineer is troubleshooting an AWS Glue ETL job that fails with an access denied error when writing to an S3 bucket. The Glue job uses an IAM role that has an S3 bucket policy attached. The bucket policy denies access to any principal that does not use server-side encryption. What is the most likely cause of the failure?
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 Glue job is not using server-side encryption when writing to S3.
Option C is correct because if the Glue job does not set the encryption header (or the role does not have the kms:GenerateDataKey permission for SSE-KMS), the bucket policy will deny the request. Option A is wrong because Glue requires permissions on the S3 bucket and KMS key. Option B is wrong because VPC endpoints do not cause access denied errors for encryption. Option D is wrong because S3 Block Public Access does not deny write access to authorized roles.
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 VPC endpoint policy for S3 is too restrictive.
Why it's wrong here
VPC endpoint policies control access through the endpoint, but the error is from the bucket policy.
✗
The IAM role does not have s3:PutObject permission.
Why it's wrong here
The error is likely due to encryption enforcement, not lack of base permission.
✓
The Glue job is not using server-side encryption when writing to S3.
Why this is correct
The bucket policy denies requests without encryption, causing access denied even if the role has PutObject permission.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The S3 bucket uses S3 Block Public Access which denies all writes.
Why it's wrong here
S3 Block Public Access prevents public access, not authorized writes.
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.
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.
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 Glue job is not using server-side encryption when writing to S3. — Option C is correct because if the Glue job does not set the encryption header (or the role does not have the kms:GenerateDataKey permission for SSE-KMS), the bucket policy will deny the request. Option A is wrong because Glue requires permissions on the S3 bucket and KMS key. Option B is wrong because VPC endpoints do not cause access denied errors for encryption. Option D is wrong because S3 Block Public Access does not deny write access to authorized roles.
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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