The answer is that the Lambda execution role lacks permissions to create log groups and write logs. This is the most likely reason for missing CloudWatch logs because the AWS CLI output shows the log group exists but has zero stored bytes, meaning the Lambda function successfully invoked but failed to write any log events. Without the necessary IAM permissions—specifically `logs:CreateLogGroup`, `logs:CreateLogStream`, and `logs:PutLogEvents`—the function cannot deliver logs to CloudWatch, even though the log group itself was pre-created. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Lambda’s execution role and its dependency on CloudWatch Logs permissions; a common trap is assuming the log group’s existence guarantees logs are being written. Remember the memory tip: “No logs, no role—check the policy for the log control.”
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. 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.
Network Topology
Refer to the exhibit. A data engineer is troubleshooting an AWS Lambda function that processes data from Amazon S3. The function is triggered by S3 events, but no logs appear in CloudWatch Logs. The engineer runs the AWS CLI command shown. What is the MOST likely reason for the missing logs?
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 Lambda execution role does not have permissions to create log groups and write logs.
Option B is correct because the log group shows 'storedBytes': 0, indicating no logs have been written. The most common cause is that the Lambda execution role lacks permission to create log streams and put logs. Option A is wrong because the log group exists. Option C is wrong because retention does not prevent logs from being written. Option D is wrong because the CLI command shows the log group exists.
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 Lambda execution role does not have permissions to create log groups and write logs.
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The Lambda function is configured to log to a different log group.
Why it's wrong here
The CLI shows the log group with the expected name.
✗
The Lambda function is not being invoked by S3 events.
Why it's wrong here
If not invoked, no log group would exist; but group exists.
✗
The log retention policy is set to 7 days, causing logs to expire immediately.
Why it's wrong here
Retention does not prevent writing.
Common exam traps
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.
Trap categories for this question
Command / output trap
The CLI shows the log group with the expected name.
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 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.
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Lambda execution role does not have permissions to create log groups and write logs. — Option B is correct because the log group shows 'storedBytes': 0, indicating no logs have been written. The most common cause is that the Lambda execution role lacks permission to create log streams and put logs. Option A is wrong because the log group exists. Option C is wrong because retention does not prevent logs from being written. Option D is wrong because the CLI command shows the log group exists.
What should I do if I get this DEA-C01 question wrong?
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.
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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Question Discussion
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