DEA-C01 Data Store Management Practice Question
A data engineer is using Amazon Athena to query data stored in an S3 bucket. The queries are running slowly. Which THREE actions can improve query performance?
⚠ Common exam trap
Many exam-takers think S3 storage class (Standard-IA) affects query performance, but Athena's performance is independent of storage class; the key levers are data format, partitioning, and compression.
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
✓
Partition the data on commonly filtered columns.
Partitioning data on commonly filtered columns (Option A) improves Athena query performance by reducing the amount of data scanned. Athena uses Hive-style partitioning (e.g., `s3://bucket/table/year=2023/month=01/`), and when a query includes a filter on the partition column, Athena prunes partitions and only reads the relevant S3 prefixes. This directly reduces I/O and query cost, as Athena charges per TB of data scanned.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Partition the data on commonly filtered columns.
Why this is correct
Partition pruning reduces amount of data scanned.
- ✗
Convert the data to JSON format for better schema evolution.
Why it's wrong here
JSON is text-based and larger, slowing queries.
- ✗
Move the data to S3 Standard-IA storage class.
Why it's wrong here
Storage class does not affect query performance.
- ✓
Convert the data to a columnar format such as Parquet or ORC.
Why this is correct
Columnar formats reduce I/O and improve compression.
- ✓
Use compression (e.g., Snappy, Gzip) on the data files.
Why this is correct
Compression reduces data size and I/O.
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.