DEA-C01 Data Operations and Support Practice Question
A data engineer is running an Amazon Athena query that scans a large amount of data in Amazon S3, resulting in high costs. The data is stored in Parquet format in a partitioned table. Which strategy would be MOST effective in reducing the amount of data scanned?
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
✓
Ensure the query includes a WHERE clause that filters on partition columns.
Partition pruning allows Athena to read only the partitions that match the WHERE clause, significantly reducing the amount of data scanned. Option A is correct because filtering on partition columns is the most effective way to minimize scanned data. Option B is incorrect because Parquet is a columnar format that already compresses well and reduces scan compared to CSV with GZIP. Option C is incorrect because S3 Intelligent-Tiering optimizes storage costs, not query scan costs. Option D is incorrect because adding more partition columns does not reduce scan unless the query filters on them, and may increase metadata overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Ensure the query includes a WHERE clause that filters on partition columns.
Why this is correct
Partition pruning reduces the amount of data scanned.
- ✗
Convert the Parquet files to CSV format and apply GZIP compression.
Why it's wrong here
CSV is less efficient than Parquet and increases scan.
- ✗
Use S3 Intelligent-Tiering storage class to reduce storage costs.
Why it's wrong here
Storage class does not affect query scan size.
- ✗
Increase the number of partitions by adding more partition columns.
Why it's wrong here
More partitions alone do not reduce scan without filtering.
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.