DEA-C01 Data Store Management Practice Question
A data engineer manages an Amazon S3 data lake with millions of small JSON files ingested continuously. Amazon Athena queries over this data are slow and expensive because each query scans many small objects. The engineer wants to improve query performance and reduce cost without changing the data content. Which solution should the engineer implement?
⚠ Common exam trap
The trap here is assuming that S3 storage-class or transfer features can improve Athena query performance, when the real issue is file format and object count.
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 AWS Glue ETL to compact the small files into larger Parquet files partitioned by common query filters.
The scenario describes slow and costly Athena queries caused by many small JSON files. Compacting into larger Parquet files and partitioning by common filters reduces the number of objects scanned and leverages columnar storage to scan less data. This directly improves performance and lowers cost without changing data content, making it the correct solution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use AWS Glue ETL to compact the small files into larger Parquet files partitioned by common query filters.
Why this is correct
Compacting small JSON files into larger Parquet files reduces the number of objects Athena must list and open, and Parquet's columnar format allows Athena to scan only needed columns. Partitioning by common filters further reduces data scanned. This directly addresses both performance and cost without altering the underlying data semantics, making it the most effective solution for this scenario.
- ✗
Increase the Athena query result reuse cache TTL to 7 days.
Why it's wrong here
Athena query result reuse can cache identical queries, but with continuously ingested data and varied queries, the cache hit rate would be low. It does not address the root cause of many small files and full scans. Extending TTL alone will not significantly improve performance or reduce cost for this dynamic dataset.
- ✗
Convert the S3 bucket to S3 Intelligent-Tiering to improve read throughput.
Why it's wrong here
S3 Intelligent-Tiering automatically moves objects between access tiers to optimize storage cost, not read throughput. It does not change object count or format, so Athena still scans many small JSON files. This option fails to address the core issue of inefficient file layout and will not improve query performance or reduce scanned bytes.
- ✗
Enable S3 Transfer Acceleration on the bucket to speed up Athena query reads.
Why it's wrong here
S3 Transfer Acceleration speeds up uploads and downloads over long distances by using AWS edge locations, but it does not optimize how Athena reads and scans objects. It does not reduce the number of small files or the bytes scanned per query, so it will not improve Athena query performance or lower query costs in this scenario.
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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JA
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.