The answer is the VPC endpoint policy overriding the bucket policy allow. This is correct because when an S3 bucket is accessed through a VPC endpoint, the request must pass both the bucket policy and the VPC endpoint policy; the endpoint policy acts as an additional layer of authorization that can explicitly deny actions even if the bucket policy grants them, and since an explicit deny in any policy overrides any allow, the request from the IAM role is blocked. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how policy evaluation logic works across multiple policy documents, particularly the often-overlooked VPC endpoint policy that can silently deny access. A common trap is assuming that a bucket policy allow is sufficient, but you must remember that endpoint policies are evaluated separately and can deny traffic from within the VPC. Memory tip: think of the VPC endpoint policy as a bouncer at a private door—even if the bucket’s main door policy says “welcome,” the bouncer can still say “no entry.”
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 has an S3 bucket policy that allows access to a specific IAM role. However, an administrator notices that requests from that role are being denied. The bucket is encrypted with AES-256. What is the MOST likely reason for the denial?
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 bucket policy allows access, but the VPC endpoint policy denies the action.
Option B is correct because even if the bucket policy allows access, if the bucket is not publicly accessible and the VPC endpoint policy does not allow the action, access will be denied. Option A is wrong because AES-256 encryption does not require additional permissions. Option C is wrong because an explicit deny in the bucket policy would override an allow. Option D is wrong because S3 Block Public Access settings affect only public access, not IAM role access.
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 IAM role does not have s3:Decrypt permission on the bucket.
Why it's wrong here
AES-256 is server-side encryption and does not require decryption permissions.
✗
The bucket policy has an explicit deny statement that overrides the allow.
Why it's wrong here
The question states the policy allows access, so an explicit deny would contradict that.
✓
The bucket policy allows access, but the VPC endpoint policy denies the action.
Why this is correct
A VPC endpoint policy can restrict actions even if the bucket policy allows them.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The S3 Block Public Access settings are blocking the request.
Why it's wrong here
Block Public Access only affects public access, not IAM role access.
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 bucket policy allows access, but the VPC endpoint policy denies the action. — Option B is correct because even if the bucket policy allows access, if the bucket is not publicly accessible and the VPC endpoint policy does not allow the action, access will be denied. Option A is wrong because AES-256 encryption does not require additional permissions. Option C is wrong because an explicit deny in the bucket policy would override an allow. Option D is wrong because S3 Block Public Access settings affect only public access, not IAM role access.
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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