The answer is that the Lambda execution role lacks the necessary permissions to write logs to CloudWatch. Even when a log group exists, a Lambda function cannot create log streams or send log events without the `logs:CreateLogStream` and `logs:PutLogEvents` actions granted in its IAM role; without these, the function may run silently but produce zero storedBytes because no log data is ever delivered. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how Lambda’s execution environment interacts with CloudWatch Logs, often appearing as a trick where a pre-existing log group misleads you into thinking permissions are fine. A common trap is assuming the log group’s existence confirms write access, but the real issue is the missing stream-level permissions. Memory tip: “No streams, no writes—check the role’s rights.”
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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 Lambda function named 'IngestionProcessor' is failing. The engineer checks CloudWatch Logs and sees the log group exists but storedBytes is 0. Why might the logs show no data?
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 permission to write logs to CloudWatch
The log group exists but has no log streams, meaning the function hasn't executed (or its execution role lacks logs:CreateLogStream and logs:PutLogEvents). The most common cause is missing IAM permissions for CloudWatch Logs.
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 permission to write logs to CloudWatch
Why this is correct
Without logs:CreateLogGroup, CreateLogStream, PutLogEvents, logs are not written.
Related concept
Read the scenario before looking for a memorised answer.
✗
The Lambda function is configured with a dead letter queue
Why it's wrong here
DLQ does not prevent log writing.
✗
The Lambda function has not been invoked yet
Why it's wrong here
The function is failing, so it should have been invoked.
✗
The log group is encrypted with a KMS key and the Lambda function lacks decrypt permission
Why it's wrong here
If the log group is encrypted, but storedBytes 0 suggests no attempts; permission issue is more fundamental.
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.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 Ingestion and Transformation — This question tests Data Ingestion and Transformation — 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 permission to write logs to CloudWatch — The log group exists but has no log streams, meaning the function hasn't executed (or its execution role lacks logs:CreateLogStream and logs:PutLogEvents). The most common cause is missing IAM permissions for CloudWatch Logs.
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.
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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