The correct answer is the bucket policy that grants s3:GetObject access to the destination account’s root principal, because cross-account S3 access requires a resource-based policy (the bucket policy) to explicitly authorize a principal from another AWS account. An IAM policy alone in the destination account is insufficient—it must be paired with a bucket policy that lists the external account as the Principal. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this tests your understanding of the fundamental distinction between resource-based and identity-based policies for cross-account scenarios. A common trap is thinking an IAM policy in the destination account is enough, but without the bucket policy allowing the cross-account principal, the request is denied. Remember the memory tip: “Bucket policy for the guest, IAM policy for the host”—the bucket owner writes the bucket policy to invite the external account, while the external account uses its own IAM policy to exercise that permission.
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. 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 DevOps engineer needs to grant cross-account access to an S3 bucket. The source account is 111111111111 and the destination account is 222222222222. Which policy should be attached to the S3 bucket?
Option C is correct because it uses a bucket policy to grant cross-account access to the S3 bucket. The policy specifies the destination account (222222222222) as the principal, allowing s3:GetObject on the bucket's objects. This is the standard AWS approach for cross-account S3 access, as bucket policies can grant permissions to principals in other AWS accounts.
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.
✗
Attach an IAM policy to the user in account 111111111111 allowing s3:GetObject.
Why it's wrong here
IAM policy only grants access within the same account.
✗
Set the bucket ACL to grant full control to account 222222222222.
Why it's wrong here
ACLs are not recommended; bucket policy is preferred.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse which account's ARN to use in the Principal field, mistakenly using the source account (111111111111) instead of the destination account (222222222222), or they incorrectly assume an IAM policy in the source account can grant cross-account access.
Detailed technical explanation
How to think about this question
Cross-account S3 access requires the destination account's IAM user or role to have an IAM policy allowing the action (e.g., s3:GetObject), and the source account's bucket policy must explicitly grant access to the destination account's root or a specific principal. The bucket policy's Principal element uses the ARN of the destination account's root (arn:aws:iam::222222222222:root), which effectively delegates permission to all IAM users/roles in that account, provided they have an allow policy. This two-way permission model ensures both the resource-based policy (bucket policy) and the identity-based policy (IAM policy) align.
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 and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: {"Version":"2012-10-17","Statement":[{"Effect":"Allow","Principal":{"AWS":"arn:aws:iam::222222222222:root"},"Action":"s3:GetObject","Resource":"arn:aws:s3:::example-bucket/*"}]} — Option C is correct because it uses a bucket policy to grant cross-account access to the S3 bucket. The policy specifies the destination account (222222222222) as the principal, allowing s3:GetObject on the bucket's objects. This is the standard AWS approach for cross-account S3 access, as bucket policies can grant permissions to principals in other AWS accounts.
What should I do if I get this DOP-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.
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. An organization wants to grant cross-account access to an S3 bucket in Account A to a user in Account B. Which policy configuration is required?
easy
✓ A.A bucket policy in Account A and an IAM user policy in Account B
B.An S3 bucket ACL granting access to the user in Account B
C.An IAM user policy in Account B allowing access to the bucket
D.A bucket policy in Account A granting access to the user in Account B
Why A: Cross-account access requires both a bucket policy in Account A granting access to the user in Account B and an IAM user policy in Account B allowing the user to access the bucket. Option A is wrong because only bucket policy is insufficient. Option C is wrong because only IAM policy is insufficient. Option D is wrong because ACLs are legacy and not recommended.
Variation 2. A DevOps engineer needs to grant cross-account access to an S3 bucket in Account A for a user in Account B. Which combination of policies is required?
easy
✓ A.An S3 bucket policy in Account A and an IAM policy in Account B.
B.An IAM role in Account A and an IAM policy in Account B.
C.Only an IAM policy in Account B.
D.Only an S3 bucket policy in Account A.
Why A: An S3 bucket policy in Account A granting access to Account B's user, and an IAM user policy in Account B allowing access to the bucket. Option C is correct.
Variation 3. A DevOps engineer needs to grant cross-account access to an S3 bucket in Account A for users in Account B. The users in Account B must be able to list objects and read them. What is the most secure way to configure this access?
medium
A.Create a bucket policy in Account A that grants access to the IAM user ARNs from Account B.
B.Create a KMS key in Account A and share it with Account B to decrypt objects.
✓ C.Create a bucket policy in Account A granting access to the root user of Account B, and create an IAM policy in Account B allowing the users to access the bucket.
D.Create an IAM role in Account A with trust policy allowing Account B to assume it, and attach a policy granting S3 access.
Why C: Option C is correct because it combines a bucket policy in Account A granting access to Account B's root or specific ARN, and an IAM policy in Account B allowing users to access that bucket. Option A is wrong because a bucket policy alone is insufficient; Account B users also need IAM permissions. Option B is wrong because an IAM role in Account A with a trust policy from Account B is a common pattern, but the question specifies users in Account B, so the role approach works but requires users to assume the role; option C is more direct for S3 access. Option D is wrong because KMS is for encryption, not access control.
Variation 4. A DevOps engineer needs to grant cross-account access to an S3 bucket. The source account is 111111111111 and the target account is 222222222222. Which combination of a bucket policy and an IAM policy correctly grants the target account access?
easy
A.Bucket policy: { "Effect": "Allow", "Principal": "222222222222", "Action": "s3:GetObject", "Resource": "arn:aws:s3:::example-bucket/*" } and IAM policy: same as A
Why B: Cross-account S3 access requires a bucket policy in the source account that grants permissions to the target account's root or a specific role, and an IAM policy in the target account that allows the user to access the bucket. Option A is correct. Option B is missing the bucket policy. Option C is missing the IAM policy. Option D uses an incorrect syntax.
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Question Discussion
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