DEA-C01 Data Ingestion and Transformation Practice Question
A data engineer is building an AWS Glue ETL job that reads JSON files from Amazon S3, flattens nested arrays, and writes Parquet to another S3 bucket. The job runs daily and processes about 2 TB. The engineer notices that job runs are failing intermittently with OutOfMemory errors during the shuffle phase. The job uses 10 G.1X workers. Which change should the engineer make to resolve the memory failures while minimizing cost?
⚠ Common exam trap
The trap here is assuming that adding more small workers or changing the input format will fix shuffle memory errors, when the issue is per-executor memory that only a larger worker type resolves.
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
✓
Switch the worker type to G.2X to provide more memory and disk per worker.
OutOfMemory errors during the shuffle phase of a Glue job indicate insufficient per-worker memory. G.2X workers provide double the memory and disk of G.1X, which is the most direct and cost-effective fix for shuffle-heavy transformations such as flattening nested arrays. Reducing workers or changing the source format does not address the memory bottleneck and can worsen the problem.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Reduce the number of workers from 10 to 5 to lower concurrency.
Why it's wrong here
Reducing workers decreases total cluster memory and parallelism, which would make OutOfMemory errors more likely, not less. Fewer workers means each worker processes more data and more shuffle partitions land on fewer executors. This change would worsen the memory pressure and likely cause the job to fail more frequently or run much longer.
- ✗
Convert the source JSON files to CSV before running the Glue job.
Why it's wrong here
Converting JSON to CSV is a separate transformation that does not reduce the in-memory footprint of the shuffle during array flattening. The Glue job still needs to explode nested arrays, which is the memory-intensive step. Adding a pre-conversion step increases pipeline complexity and cost without addressing the root cause of the OutOfMemory error during shuffle.
- ✗
Enable AWS Glue job bookmarks to skip previously processed files.
Why it's wrong here
Job bookmarks track which S3 objects have already been processed so subsequent runs skip them. While bookmarks improve incremental processing, they do not address in-memory shuffle pressure during a single run. The OutOfMemory error occurs while processing data within a run, so enabling bookmarks would not prevent the failure and could even cause data to be skipped incorrectly.
- ✓
Switch the worker type to G.2X to provide more memory and disk per worker.
Why this is correct
G.2X workers provide twice the memory and disk of G.1X workers, which directly addresses OutOfMemory failures during shuffle-intensive operations like flattening nested arrays. Because the job is memory-bound rather than CPU-bound, increasing per-worker memory is the most targeted fix. Keeping the worker count the same with larger workers often costs less than adding many small workers for shuffle-heavy workloads.
Visual reference
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 |
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.