MLS-C01 Data Engineering Practice Question
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.)
⚠ Common exam trap
Candidates often assume Kinesis Data Firehose provides exactly-once delivery to S3, but it actually provides at-least-once. Also, the Kinesis Producer Library (KPL) provides at-least-once with deduplication, not exactly-once.
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.
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.
- ✗
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.
- ✗
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.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This MLS-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 MLS-C01 exam.