The answer is that an explicit Deny overrides any Allow because IAM evaluates explicit Deny before Allow. This is the core of AWS’s default-deny, then allow-override, then explicit-deny model: once an explicit Deny is found, the evaluation stops and access is blocked, regardless of any other Allow statements in the same policy or in attached identity-based policies. On the AWS Certified Developer Associate DVA-C02 exam, this concept frequently appears in troubleshooting scenarios where a developer sees an Allow for s3:PutObject but still gets a 403 error—the trap is assuming that an Allow will always win. Instead, remember that an explicit Deny is the ultimate override, acting as a hard block that cannot be bypassed by any other permission. A useful memory tip is “Deny is the final word”—once AWS finds an explicit Deny, it stops evaluating and denies the request immediately.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. 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 developer is troubleshooting an S3 bucket policy that is denying all access. The policy has an explicit Deny for s3:PutObject. What is the most likely reason for the denial even though an Allow exists?
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
✓
IAM evaluates explicit Deny before Allow.
IAM evaluates explicit Deny before Allow, so an explicit Deny overrides any Allow.
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 bucket policy has an explicit Deny for all actions.
Why it's wrong here
The Deny is only for s3:PutObject, not all actions.
✗
The user is not authorized because the bucket is in a different account.
Why it's wrong here
Cross-account access requires proper permissions, but the Deny is the immediate issue.
✓
IAM evaluates explicit Deny before Allow.
Why this is correct
Explicit Deny always overrides Allow.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The AWS account root user has denied access.
Why it's wrong here
Root user can override, but not typical for a bucket policy.
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 DVA-C02 ACL questions on filtering logic and placement.
Security — This question tests Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: IAM evaluates explicit Deny before Allow. — IAM evaluates explicit Deny before Allow, so an explicit Deny overrides any Allow.
What should I do if I get this DVA-C02 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 DVA-C02 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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A developer is troubleshooting access to an S3 bucket from an EC2 instance. The instance has an IAM role with an attached policy that allows s3:GetObject on the bucket. However, the application is receiving Access Denied errors. What is a likely cause?
hard
A.The IAM role does not have s3:ListBucket permission.
B.The EC2 instance is not associated with an instance profile.
✓ C.The bucket policy has an explicit deny that overrides the IAM allow.
D.The bucket has S3 Block Public Access enabled.
Why C: Option C is correct because if the bucket policy explicitly denies access, the deny overrides any allow from IAM. Option A is wrong because S3 does not require S3 Block Public Access for IAM role access. Option B is wrong because the instance profile needs an IAM role, not an IAM user. Option D is wrong because S3 does not require the s3:ListBucket permission to get an object if you know the key.
Last reviewed: Jun 20, 2026
Question Discussion
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This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.
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