DEA-C01 Data Operations and Support Practice Question
Which TWO actions should a data engineer take to optimize Amazon S3 query performance for Amazon Athena when dealing with large Parquet files? (Choose 2.)
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
✓
Optimize file sizes to be around 64 MB to 256 MB
The correct answers are D and E. Optimizing file sizes to be around 64 MB to 256 MB (D) reduces the overhead of Athena reading many small files or processing overly large files, balancing parallelism and efficiency. Partitioning data by frequently filtered columns (E) allows Athena to prune partitions and scan less data, improving query performance. Option A (single large file) hinders parallelism and query performance. Option B (GZIP compression) is already supported by Parquet and does not inherently optimize query performance beyond the file size considerations. Option C (many small files) increases metadata overhead and degrades 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.
- ✗
Store data in a single large file without partitioning
Why it's wrong here
Without partitioning, full scan is required.
- ✗
Use GZIP compression on the Parquet files
Why it's wrong here
Parquet already has internal compression; GZIP adds overhead.
- ✗
Split large files into many small files
Why it's wrong here
Small files increase metadata overhead and reduce performance.
- ✓
Optimize file sizes to be around 64 MB to 256 MB
Why this is correct
Optimal file size improves parallelism and performance.
- ✓
Partition the data by frequently filtered columns
Why this is correct
Partition pruning limits data scanned.
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.