DEA-C01 Data Ingestion and Transformation Practice Question
A data engineer notices that an AWS Glue ETL job is running slower than expected. The job reads from Amazon S3, joins two datasets, and writes the result back to S3. The job uses the default worker type (G.1X) and 10 DPUs. Which action is most likely to improve performance?
⚠ Common exam trap
Watch out — candidates often assume more DPUs or a larger worker type always speeds up a job, but the DEA-C01 exam tests understanding that shuffle optimization (like repartitioning) is the most impactful fix for join performance issues.
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
✓
Repartition the data before the join operation
The default G.1X worker type provides 16 GB of memory and 4 vCPUs per DPU. With 10 DPUs, the job likely has sufficient compute but suffers from data skew or inefficient partitioning during the join. Repartitioning the data before the join ensures that keys are evenly distributed across partitions, reducing shuffle overhead and preventing straggler tasks, which directly improves performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the number of DPUs to 20
Why it's wrong here
Could help but not as targeted as repartitioning.
- ✓
Repartition the data before the join operation
Why this is correct
Optimizes parallelism and reduces shuffling.
- ✗
Use coalesce to reduce the number of output files
Why it's wrong here
Reduces parallelism, likely making performance worse.
- ✗
Change the worker type to G.2X
Why it's wrong here
More memory per worker but does not address partition skew.
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 DEA-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 DEA-C01 exam.