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 needs to grant cross-account access to an S3 bucket for an IAM user from another AWS account. The developer has added a bucket policy that allows the user's ARN. However, the user still cannot access the bucket. What additional step is required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The user must have an IAM policy allowing the required S3 actions on that bucket
A is correct because cross-account access to an S3 bucket requires both a resource-based policy (the bucket policy) that grants access to the user's ARN and an identity-based policy (an IAM policy attached to the user) that explicitly allows the required S3 actions on that bucket. Without the IAM policy, the user's account denies the request by default, even if the bucket policy permits it. This is the principle of 'permission delegation' in AWS: the resource owner can grant access, but the user's own account must also authorize the action.
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 user must have an IAM policy allowing the required S3 actions on that bucket
Why this is correct
Without an identity-based policy, the user is not allowed to perform the action even if the resource policy permits it.
Related concept
Read the scenario before looking for a memorised answer.
✗
The bucket must be made public
Why it's wrong here
Making the bucket public would bypass the need for IAM policies but violates security best practices and is not required.
✗
The user must use a different AWS CLI profile
Why it's wrong here
Using a different profile does not resolve the missing IAM policy.
✗
The resource-based policy must explicitly allow the user's ARN
Why it's wrong here
The bucket policy already allows the user's ARN; the missing piece is the user's IAM policy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a bucket policy alone is sufficient for cross-account access, forgetting that the requesting account must also explicitly authorize the action via an IAM policy, which is a common oversight in AWS cross-account scenarios.
Detailed technical explanation
How to think about this question
Under the hood, AWS evaluates access using a combination of identity-based and resource-based policies, with the effective permission being the union of all allowed actions minus any explicit denies. For cross-account access, the bucket policy acts as a 'grant' from the resource owner, but the user's IAM policy must also allow the action; if either policy denies or lacks an allow, the request fails. A real-world scenario is when a developer sets up a bucket policy for a partner account but forgets to attach the corresponding IAM policy to the partner's user, leading to 'AccessDenied' errors despite the bucket policy appearing correct.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 user must have an IAM policy allowing the required S3 actions on that bucket — A is correct because cross-account access to an S3 bucket requires both a resource-based policy (the bucket policy) that grants access to the user's ARN and an identity-based policy (an IAM policy attached to the user) that explicitly allows the required S3 actions on that bucket. Without the IAM policy, the user's account denies the request by default, even if the bucket policy permits it. This is the principle of 'permission delegation' in AWS: the resource owner can grant access, but the user's own account must also authorize the action.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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