Quick Answer
The answer is that the S3 bucket policy does not allow CloudTrail to write logs. Even when CloudTrail data event selectors are correctly configured with a trailing slash for the S3 prefix ARN, such as arn:aws:s3:::my-bucket/logs/, CloudTrail must have explicit write permissions granted via the destination bucket’s resource-based policy. Without a bucket policy statement that grants the CloudTrail service principal s3:PutObject access to the specified prefix, data events for objects under that prefix will silently fail to log. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding that CloudTrail logging depends on both the trail configuration and the target bucket’s permissions—a common trap is assuming a correctly formatted prefix ARN alone guarantees logging. Remember the two-step check: verify the selector format first, then confirm the bucket policy grants CloudTrail write access. A helpful mnemonic is “ARN plus Allow” — a valid ARN is useless without an explicit Allow in the bucket policy.
This DEA-C01 practice question tests your understanding of data security and governance. 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.
Refer to the exhibit. A data engineer configured CloudTrail to log data events for an S3 bucket. However, the engineer notices that no data events are being logged for objects in the 'logs/' prefix. 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.
The S3 bucket policy does not allow CloudTrail to write logs
CloudTrail needs a bucket policy granting s3:PutObject.
The data resource should specify the bucket ARN without a prefix
Why wrong: Prefixes are supported.
The prefix 'logs/' must not include a trailing slash
Why wrong: Trailing slash is required.
Data events are not supported for S3
Why wrong: They are supported.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The S3 bucket policy does not allow CloudTrail to write logs
The data resource value is missing a trailing slash (should be 'logs/')? Actually it has a trailing slash. Wait, the issue is that the ARN is for a prefix, but CloudTrail data event selectors for S3 require a bucket ARN or prefix ARN with a trailing slash. The provided ARN 'arn:aws:s3:::my-bucket/logs/' is correct format. However, the likely issue is that the bucket is in a different region, but the trail is in a different region? No, more common: the IAM role for CloudTrail lacks permissions to log to S3. But the exhibit shows a correct selector. Actually, common mistake: the selector must have a trailing slash, which it does. The most likely cause is that the trail is not logging because the S3 bucket policy does not grant CloudTrail write access. Option A is plausible. Option B is wrong because prefix is correct. Option C is wrong because it includes trailing slash. Option D is wrong because data events are enabled. So option A is correct.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The S3 bucket policy does not allow CloudTrail to write logs
Why this is correct
CloudTrail needs a bucket policy granting s3:PutObject.
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 data resource should specify the bucket ARN without a prefix
Why it's wrong here
Prefixes are supported.
The prefix 'logs/' must not include a trailing slash
Why it's wrong here
Trailing slash is required.
Data events are not supported for S3
Why it's wrong here
They are supported.
Common exam traps
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
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which DEA-C01 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.
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FAQ
Data Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
The correct answer is: The S3 bucket policy does not allow CloudTrail to write logs — The data resource value is missing a trailing slash (should be 'logs/')? Actually it has a trailing slash. Wait, the issue is that the ARN is for a prefix, but CloudTrail data event selectors for S3 require a bucket ARN or prefix ARN with a trailing slash. The provided ARN 'arn:aws:s3:::my-bucket/logs/' is correct format. However, the likely issue is that the bucket is in a different region, but the trail is in a different region? No, more common: the IAM role for CloudTrail lacks permissions to log to S3. But the exhibit shows a correct selector. Actually, common mistake: the selector must have a trailing slash, which it does. The most likely cause is that the trail is not logging because the S3 bucket policy does not grant CloudTrail write access. Option A is plausible. Option B is wrong because prefix is correct. Option C is wrong because it includes trailing slash. Option D is wrong because data events are enabled. So option A is correct.
Identify which DEA-C01 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.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 20, 2026
This DEA-C01 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 DEA-C01 exam.
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