DEA-C01 Data Ingestion and Transformation Practice Question
A company ingests millions of small files (1-10 KB) into Amazon S3 every hour. These files are then processed by AWS Glue ETL jobs. The Glue jobs are slow because of the overhead of reading many small files. Which strategy will most effectively improve Glue job performance?
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 a Lambda function to merge small files into larger ones before Glue processes them.
Grouping small files into larger ones (e.g., by merging in a preprocessing step) reduces the number of file read operations and improves Glue's efficiency. Using S3 Select or increasing DPUs helps but doesn't address the root cause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Glue job bookmark.
Why it's wrong here
Job bookmarks are for incremental processing, not for handling small file overhead.
- ✗
Increase the number of DPUs for the Glue job.
Why it's wrong here
More DPUs help parallelism but the overhead of opening many small files remains.
- ✗
Use S3 Select to filter data before Glue reads it.
Why it's wrong here
S3 Select can reduce data scanned but doesn't reduce the overhead of opening many small files.
- ✓
Use a Lambda function to merge small files into larger ones before Glue processes them.
Why this is correct
Merging files reduces the number of objects, speeding up Glue's list and read operations.
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 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.