- A
Set up an S3 event notification to trigger the Lambda function on object creation.
Why wrong: This triggers Lambda after data is written, not before.
- B
Configure a Lambda function as a data transformation source in the Firehose delivery stream.
This enables Firehose to invoke Lambda for transformation.
- C
Ensure the Lambda function returns the transformed data in the format required by Firehose.
Firehose expects a specific response format from the Lambda function.
- D
Subscribe the Lambda function to the CloudWatch Logs log group for the Firehose stream.
Why wrong: This is for monitoring, not for data transformation.
- E
Have the Lambda function write the transformed data directly to the S3 bucket.
Why wrong: This bypasses Firehose and is not the intended design.
Quick Answer
The correct answer involves two essential steps: configuring Firehose to invoke the Lambda function for transformation and ensuring the Lambda function returns transformed data in the exact format Firehose requires. This is because Kinesis Data Firehose acts as a delivery stream that can natively call a Lambda function on incoming records before writing them to S3, but the function must respond with a structured payload containing a record ID, a result status like "Ok" or "Dropped", and the transformed data base64-encoded. On the AWS Certified Data Engineer Associate DEA-C01 exam, this tests your understanding of the Firehose Lambda transformation setup as a serverless ingestion pattern, often appearing in scenario-based questions where candidates mistakenly think Firehose can handle complex transformations natively or that Lambda can return raw JSON without the required envelope. A common trap is forgetting the base64 encoding step, which causes the transformation to silently fail. Remember the mnemonic "RIB" — Record ID, result status, and Base64 data — to recall the three required fields in the Lambda response.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 data engineer is designing a serverless data ingestion pipeline that uses Amazon Kinesis Data Firehose to deliver data to Amazon S3. The data must be transformed using AWS Lambda before being written to S3. Which two steps are required to enable this transformation? (Select TWO.)
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
Configure a Lambda function as a data transformation source in the Firehose delivery stream.
Option B is correct because Amazon Kinesis Data Firehose can be configured to invoke a Lambda function as a data transformation source. This allows Firehose to pass incoming records to the Lambda function, which processes and returns the transformed records before they are delivered to the S3 destination. Option C is correct because the Lambda function must return data in the specific format that Firehose expects, including a record ID, result status, and base64-encoded data, otherwise the transformation will fail.
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.
- ✗
Set up an S3 event notification to trigger the Lambda function on object creation.
Why it's wrong here
This triggers Lambda after data is written, not before.
- ✓
Configure a Lambda function as a data transformation source in the Firehose delivery stream.
Why this is correct
This enables Firehose to invoke Lambda for transformation.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Ensure the Lambda function returns the transformed data in the format required by Firehose.
Why this is correct
Firehose expects a specific response format from the Lambda function.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Subscribe the Lambda function to the CloudWatch Logs log group for the Firehose stream.
Why it's wrong here
This is for monitoring, not for data transformation.
- ✗
Have the Lambda function write the transformed data directly to the S3 bucket.
Why it's wrong here
This bypasses Firehose and is not the intended design.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse post-delivery transformations (using S3 event notifications) with in-stream transformations (using Firehose's built-in Lambda integration), leading them to select Option A instead of the correct Firehose-specific configuration.
Detailed technical explanation
How to think about this question
When Firehose invokes a Lambda function for transformation, it sends a batch of records as a payload with each record containing base64-encoded data. The Lambda function must return a response with the same number of records, each including a 'recordId' (matching the input), a 'result' field (Ok, Dropped, or ProcessingFailed), and 'data' (base64-encoded transformed data). A common subtlety is that the Lambda function must handle the 6 MB payload limit per invocation and the 300-second timeout; exceeding these can cause records to be marked as ProcessingFailed and sent to the error destination.
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.
TExam Day Tips
- 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Data Ingestion and Transformation — study guide chapter
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
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: Configure a Lambda function as a data transformation source in the Firehose delivery stream. — Option B is correct because Amazon Kinesis Data Firehose can be configured to invoke a Lambda function as a data transformation source. This allows Firehose to pass incoming records to the Lambda function, which processes and returns the transformed records before they are delivered to the S3 destination. Option C is correct because the Lambda function must return data in the specific format that Firehose expects, including a record ID, result status, and base64-encoded data, otherwise the transformation will fail.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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