DEA-C01 Data Store Management Practice Question
A company stores application logs in Amazon S3 and wants to analyze them using Amazon Athena. The logs are in JSON format and are compressed with gzip. The data engineer needs to create an Athena table that can query these logs efficiently. The logs are stored in an S3 bucket with the prefix logs/year=2023/month=10/day=15/. The engineer wants to minimize query costs and improve performance. Which action should the engineer take?
⚠ Common exam trap
The trap here is selecting a SerDe based on compression or performance assumptions rather than matching it to the actual data format, which is JSON.
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
✓
Create an external table with the JSON SerDe, specifying the S3 location as s3://bucket/logs/ and defining partitions for year, month, and day.
To query JSON logs efficiently in Athena, the table must use the JSON SerDe to parse the data correctly. Defining partitions on year, month, and day allows Athena to prune partitions based on query filters, reducing the amount of data scanned and lowering costs. The table location should point to the root prefix so that all partitions are included. This combination provides accurate parsing and cost-effective queries.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create an external table with the JSON SerDe, specifying the S3 location as s3://bucket/logs/ and using the OpenCSVSerDe for better performance.
Why it's wrong here
The OpenCSVSerDe is designed for CSV data, not JSON. Using it with JSON logs will result in incorrect parsing. The JSON SerDe is the correct choice for JSON data. This option combines the right location with the wrong SerDe, so it fails to parse the logs correctly.
- ✗
Create an external table with the CSV SerDe, specifying the S3 location as s3://bucket/logs/ and defining partitions for year, month, and day.
Why it's wrong here
The logs are in JSON format, so using the CSV SerDe will not parse the data correctly. Athena will return errors or null values. The CSV SerDe is for comma-separated values, not JSON. This option fails because it mismatches the SerDe with the data format.
- ✗
Create an external table with the JSON SerDe, specifying the S3 location as s3://bucket/logs/year=2023/month=10/day=15/ and no partitions.
Why it's wrong here
Specifying a single day's location and no partitions means Athena will only query that day's data, but the table cannot be used to query other days without creating separate tables. This does not leverage partitioning for the entire dataset and will not scale. It also does not allow partition pruning across days.
- ✓
Create an external table with the JSON SerDe, specifying the S3 location as s3://bucket/logs/ and defining partitions for year, month, and day.
Why this is correct
Creating an external table with the JSON SerDe and defining partitions allows Athena to read the JSON logs and use partition pruning to scan only relevant data. Specifying the root S3 location and adding partitions (either manually or via MSCK REPAIR) enables efficient queries and reduces cost by limiting 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 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.