The answer is to set the Lambda function’s batch size to 1 and batch window to 0, and to configure the S3 destination to use a unique key or replace behavior. This combination enforces at-most-once processing semantics because a batch size of one ensures each Lambda invocation handles a single record; if the function fails, no retry occurs since the batch window of zero prevents record accumulation, and using unique S3 keys avoids overwriting data from a previous successful write. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how Kinesis and Lambda interact with delivery guarantees—a common trap is confusing at-most-once with at-least-once, where you would enable retries or checkpointing. Remember the memory tip: “One and done, no rerun” to recall that a batch size of one and zero window eliminate reprocessing, while unique keys prevent duplicate overwrites.
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.
A data engineer is designing a data pipeline that ingests JSON data from Amazon Kinesis Data Streams and processes it using AWS Lambda. The Lambda function writes the processed data to an Amazon S3 bucket. The engineer needs to ensure at-most-once processing semantics. Which TWO configurations should the engineer implement? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use S3 PutObject with a unique object key (e.g., include a UUID) and overwrite set to false.
Options B and D are correct. B: Setting the Lambda batch size to 1 and window to 0 ensures one record per invocation, so if the function fails, it will not retry the same record (since at-most-once means no retries). D: Setting the S3 bucket to use Replace or a unique key prevents overwriting. Option A is wrong because increasing batch size increases chance of partial failures. Option C is wrong because enabling retries violates at-most-once. Option E is wrong because checkpointing is for at-least-once.
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.
✓
Use S3 PutObject with a unique object key (e.g., include a UUID) and overwrite set to false.
Why this is correct
Unique keys prevent overwriting and duplicates.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use DynamoDB for checkpointing to track processed records.
Why it's wrong here
Checkpointing is for at-least-once processing.
✗
Set the Lambda function's batch size to 100 to process records in larger batches.
Why it's wrong here
Large batches increase risk of duplicate processing on failure.
✗
Enable function-level retries in the Lambda function for transient errors.
Why it's wrong here
Retries can cause duplicate records.
✓
Set the Lambda function's batch size to 1 and the batch window to 0.
Why this is correct
Single record processing with no window ensures no duplicates.
Related concept
Read the scenario before looking for a memorised answer.
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 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: Use S3 PutObject with a unique object key (e.g., include a UUID) and overwrite set to false. — Options B and D are correct. B: Setting the Lambda batch size to 1 and window to 0 ensures one record per invocation, so if the function fails, it will not retry the same record (since at-most-once means no retries). D: Setting the S3 bucket to use Replace or a unique key prevents overwriting. Option A is wrong because increasing batch size increases chance of partial failures. Option C is wrong because enabling retries violates at-most-once. Option E is wrong because checkpointing is for at-least-once.
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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