The answer is that the bucket policy uses a service role ARN that is not a valid principal for S3 bucket policies. S3 bucket policies require the Principal element to specify an AWS account, an IAM user or role, or a federated user—service-linked roles like AWSServiceRoleForSSO are not supported as principals in resource-based policies, meaning the policy is syntactically accepted but effectively ignored. On the AWS Certified Developer Associate DVA-C02 exam, this tests your understanding of the Principal element’s constraints in S3 policies, often appearing as a trap where a valid-looking ARN is rejected because it belongs to a service-linked role rather than a standard IAM role. A common memory tip: if the ARN contains “service-role,” it is almost certainly invalid as a principal in an S3 bucket policy—stick to account IDs, IAM roles, or AWS services like “s3.amazonaws.com” instead.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. 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 that stores log files. The bucket policy grants the AWSServiceRoleForSSO service role write access. However, the logs are not being written. What is the MOST likely reason?
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 uses a service role ARN that is not a valid principal for S3 bucket policies.
Option A is correct because S3 bucket policies must grant access to the principal, and the service role is not a valid principal for S3 bucket policies. Option B is wrong because SSE-S3 does not block writes. Option C is wrong because Block Public Access does not affect service roles. Option D is wrong because ACLs are disabled by default but service roles use bucket policies.
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 has S3 Block Public Access enabled, which blocks all service role access.
Why it's wrong here
Block Public Access only blocks public access.
✓
The bucket policy uses a service role ARN that is not a valid principal for S3 bucket policies.
Why this is correct
Service roles are not valid principals in S3 bucket policies; use the service's principal instead.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The bucket ACL is set to private, which prevents service role writes.
Why it's wrong here
ACLs are not used for service roles.
✗
The bucket has default encryption enabled using SSE-S3, which prevents writes from service roles.
Why it's wrong here
SSE-S3 does not block writes.
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: The bucket policy uses a service role ARN that is not a valid principal for S3 bucket policies. — Option A is correct because S3 bucket policies must grant access to the principal, and the service role is not a valid principal for S3 bucket policies. Option B is wrong because SSE-S3 does not block writes. Option C is wrong because Block Public Access does not affect service roles. Option D is wrong because ACLs are disabled by default but service roles use bucket policies.
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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.