- A
Decrease the number of workers to reduce memory contention.
Why wrong: Fewer workers may cause memory issues to persist.
- B
Enable job bookmarks to process only new data and use a G.2X worker type for more memory.
Job bookmarks prevent reprocessing and larger workers provide more memory.
- C
Increase the schedule frequency to run the job more often with smaller data increments.
Why wrong: More frequent runs may increase overhead but not fix memory issues.
- D
Replace AWS Glue with Amazon EMR using Spark.
Why wrong: EMR also uses Spark and requires more management.
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. 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 team is building a data pipeline that ingests data from an Amazon S3 bucket, transforms it using AWS Glue, and loads it into Amazon Redshift for analysis. The Glue job runs on a schedule every hour. The team has noticed that the job takes longer than expected and sometimes fails due to memory issues. The data volume is variable, with occasional spikes. Which solution should the team implement to optimize the pipeline?
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
Enable job bookmarks to process only new data and use a G.2X worker type for more memory.
Enabling job bookmarks allows the Glue job to process only new or changed data since the last run, reducing the data volume per execution. Using the G.2X worker type provides additional memory (e.g., 16 GB per DPU vs. 4 GB for G.1X), which helps prevent out-of-memory failures during data spikes. Together, these optimizations address both the variable data volume and memory constraints without requiring a complete pipeline redesign.
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.
- ✗
Decrease the number of workers to reduce memory contention.
Why it's wrong here
Fewer workers may cause memory issues to persist.
- ✓
Enable job bookmarks to process only new data and use a G.2X worker type for more memory.
Why this is correct
Job bookmarks prevent reprocessing and larger workers provide more memory.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the schedule frequency to run the job more often with smaller data increments.
Why it's wrong here
More frequent runs may increase overhead but not fix memory issues.
- ✗
Replace AWS Glue with Amazon EMR using Spark.
Why it's wrong here
EMR also uses Spark and requires more management.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume increasing job frequency (Option C) will automatically reduce per-run data volume, but without incremental processing (job bookmarks), each run still processes the entire dataset, leading to the same memory issues and higher costs.
Detailed technical explanation
How to think about this question
AWS Glue job bookmarks track processed data using a persistent state stored in a DynamoDB table, enabling exactly-once incremental processing by comparing file timestamps or partition values. The G.2X worker type doubles the memory per DPU (from 4 GB to 16 GB) and provides additional vCPU, which is critical for handling skewed data or transformations that require large in-memory operations like aggregations or joins. In practice, memory failures often occur when a single executor runs out of heap space due to a large partition; using G.2X workers mitigates this by providing more headroom, while job bookmarks reduce the overall data shuffled per run.
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.
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.
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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: Enable job bookmarks to process only new data and use a G.2X worker type for more memory. — Enabling job bookmarks allows the Glue job to process only new or changed data since the last run, reducing the data volume per execution. Using the G.2X worker type provides additional memory (e.g., 16 GB per DPU vs. 4 GB for G.1X), which helps prevent out-of-memory failures during data spikes. Together, these optimizations address both the variable data volume and memory constraints without requiring a complete pipeline redesign.
What should I do if I get this MLS-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.
About these practice questions
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Last reviewed: Jul 4, 2026
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