The answer is the IAM role attached to the EC2 instance has a different ARN than the one specified in the bucket policy. This is correct because S3 bucket policies use the Principal element to explicitly identify which IAM entity is allowed access; if the ARN in the policy does not exactly match the ARN of the role the instance is using, the request is denied regardless of the role’s own permissions. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how resource-based policies (bucket policies) interact with identity-based policies (IAM role policies) — a common trap is assuming that an IAM role’s permissions alone are sufficient when a bucket policy is present, but S3 evaluates both, and a bucket policy’s Principal must match the caller’s ARN. Remember the memory tip: “Principal must match the principal’s ARN — if it’s not exactly the same, it’s a deny game.”
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 access to an S3 bucket from an EC2 instance. The instance has an IAM role with a policy that allows s3:GetObject on the bucket. However, the application receives an AccessDenied error. The bucket policy is as follows:
The EC2 instance is using the correct IAM role. What is the most likely cause of the error?
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 IAM role attached to the EC2 instance has a different ARN than the one specified in the bucket policy.
Option C is correct because the bucket policy explicitly allows only the role with the exact ARN 'arn:aws:iam::123456789012:role/AppRole'. If the instance's role ARN is different, the request is denied. Option A is wrong because S3 does not require SSE for GetObject. Option B is wrong because MFA is not specified in the error. Option D is wrong because IAM role policies and bucket policies are evaluated separately; an allow in the bucket policy must match the principal.
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 bucket uses default encryption with SSE-S3, and the application does not support it.
Why it's wrong here
SSE-S3 is transparent and does not cause AccessDenied.
✓
The IAM role attached to the EC2 instance has a different ARN than the one specified in the bucket policy.
Why this is correct
Mismatch in role ARN causes denial.
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 IAM role policy allows s3:GetObject, but the bucket policy also must allow it, which it does.
Why it's wrong here
Both policies allow, so this is not the issue.
✗
The bucket policy requires MFA, but the application does not provide it.
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 DVA-C02 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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The IAM role attached to the EC2 instance has a different ARN than the one specified in the bucket policy. — Option C is correct because the bucket policy explicitly allows only the role with the exact ARN 'arn:aws:iam::123456789012:role/AppRole'. If the instance's role ARN is different, the request is denied. Option A is wrong because S3 does not require SSE for GetObject. Option B is wrong because MFA is not specified in the error. Option D is wrong because IAM role policies and bucket policies are evaluated separately; an allow in the bucket policy must match the principal.
What should I do if I get this DVA-C02 question wrong?
Identify which DVA-C02 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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