DEA-C01 Data Ingestion and Transformation Practice Question
Network Topology
Refer to the exhibit. A data engineer has configured an S3 event notification to send an event to an SQS queue when objects are created in the 'incoming/' prefix. The engineer wants to trigger an AWS Lambda function to process the object. However, the Lambda function is not being invoked. What is the most likely cause?
⚠ Common exam trap
The DEA-C01 exam often tests the distinction between sending events to a queue (S3 → SQS) and actually consuming them (SQS → Lambda), so candidates mistakenly assume that simply having S3 send to SQS will automatically trigger Lambda without an explicit event source mapping.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Lambda is not configured as an event source for the SQS queue.
The Lambda function is not being invoked because the SQS queue is not configured as an event source for Lambda. Even though S3 sends events to SQS, Lambda will only poll and process messages from the queue if an event source mapping (e.g., via CreateEventSourceMapping) is established. Without this mapping, the messages sit in the queue and Lambda remains idle.
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 function lacks permission to read from the S3 bucket.
Why it's wrong here
Lambda reading S3 directly is unnecessary here because the payload arrives via SQS; missing S3 read permission would fail the function's execution, not prevent invocation. That permission matters when Lambda is triggered by S3 notifications and must fetch the object itself.
- ✓
Lambda is not configured as an event source for the SQS queue.
Why this is correct
An SQS queue only buffers messages; Lambda must be configured with the queue as an event source mapping to poll and invoke. Without that mapping, notifications accumulate unprocessed, so the function never runs despite S3 delivering events correctly.
- ✗
The SQS queue does not exist or is in a different account.
Why it's wrong here
S3 notifications to a non-existent or cross-account queue fail at configuration, so this would surface as a setup error, not silent non-invocation. The queue exists and receives events; the missing piece is an event source mapping polling it. SQS is chosen when decoupling producers from consumers is required.
- ✗
The S3 event notification filter prefix is incorrect.
Why it's wrong here
A wrong prefix would mean no events reach the queue at all, but the exhibit shows notifications firing for 'incoming/' objects. The filter is correct; the gap is that nothing polls the queue. Prefix filters are the right control when only a subset of keys should generate events.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.