- A
Use the Kinesis Producer Library (KPL) with exactly-once delivery.
Why wrong: The Kinesis Producer Library (KPL) provides at-least-once delivery with deduplication, not exactly-once delivery, so this action does not guarantee exactly-once semantics.
- B
Use AWS Glue streaming ETL with checkpointing.
AWS Glue streaming ETL with checkpointing can achieve exactly-once processing by tracking progress and writing to a transactional data lake, making this a correct action.
- C
Enable exactly-once delivery on Kinesis Data Firehose.
Why wrong: Kinesis Data Firehose does not support exactly-once delivery to S3; it provides at-least-once delivery, so this action is not correct for exactly-once semantics.
- D
Use AWS Lambda with the Kinesis trigger and enable event source mapping with RetryAttempts set to 0.
Using AWS Lambda with the Kinesis trigger and event source mapping, setting RetryAttempts to 0 ensures no retries, meaning each record is processed exactly once (failure leads to data loss), which fits exactly-once processing under the assumption that failures are acceptable.
- E
Use Amazon SQS as the event source for downstream processing.
Why wrong: Using Amazon SQS as the event source does not integrate directly with Kinesis Data Streams for this pipeline, and SQS itself provides at-least-once delivery, not exactly-once.
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 uses Amazon Kinesis Data Streams to ingest real-time transaction data. The data must be processed in near real-time and stored in Amazon S3 for long-term analytics. The engineer wants to ensure data durability and exactly-once processing semantics. Which TWO actions should the engineer take? (Choose 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
Use AWS Glue streaming ETL with checkpointing.
Correct options: B and D. AWS Glue streaming ETL with checkpointing provides exactly-once processing semantics when writing to S3 using a transactional format like Delta Lake. Setting RetryAttempts to 0 on a Lambda event source mapping ensures that each record is processed only once (no retries), which avoids duplicate processing, though failures may cause data loss. Options A and C do not guarantee exactly-once: KPL provides at-least-once with deduplication, and Kinesis Data Firehose provides at-least-once delivery to S3. Option E (Amazon SQS) is not part of the Kinesis pipeline and does not ensure exactly-once semantics.
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 the Kinesis Producer Library (KPL) with exactly-once delivery.
Why it's wrong here
The Kinesis Producer Library (KPL) provides at-least-once delivery with deduplication, not exactly-once delivery, so this action does not guarantee exactly-once semantics.
- ✓
Use AWS Glue streaming ETL with checkpointing.
Why this is correct
AWS Glue streaming ETL with checkpointing can achieve exactly-once processing by tracking progress and writing to a transactional data lake, making this a correct action.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable exactly-once delivery on Kinesis Data Firehose.
Why it's wrong here
Kinesis Data Firehose does not support exactly-once delivery to S3; it provides at-least-once delivery, so this action is not correct for exactly-once semantics.
- ✓
Use AWS Lambda with the Kinesis trigger and enable event source mapping with RetryAttempts set to 0.
Why this is correct
Using AWS Lambda with the Kinesis trigger and event source mapping, setting RetryAttempts to 0 ensures no retries, meaning each record is processed exactly once (failure leads to data loss), which fits exactly-once processing under the assumption that failures are acceptable.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use Amazon SQS as the event source for downstream processing.
Why it's wrong here
Using Amazon SQS as the event source does not integrate directly with Kinesis Data Streams for this pipeline, and SQS itself provides at-least-once delivery, not exactly-once.
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.
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 |
What to study next
Got this wrong? Here's your next step.
Identify which MLS-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.
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FAQ
Questions learners often ask
What does this MLS-C01 question test?
Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use AWS Glue streaming ETL with checkpointing. — Correct options: B and D. AWS Glue streaming ETL with checkpointing provides exactly-once processing semantics when writing to S3 using a transactional format like Delta Lake. Setting RetryAttempts to 0 on a Lambda event source mapping ensures that each record is processed only once (no retries), which avoids duplicate processing, though failures may cause data loss. Options A and C do not guarantee exactly-once: KPL provides at-least-once with deduplication, and Kinesis Data Firehose provides at-least-once delivery to S3. Option E (Amazon SQS) is not part of the Kinesis pipeline and does not ensure exactly-once semantics.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 20, 2026
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