- A
The AWS Glue crawler does not have permissions to read the S3 bucket.
Why wrong: Incorrect. Permission issues cause access denied errors, not zero results.
- B
Athena cannot query nested JSON objects.
Why wrong: Incorrect. Athena can query nested JSON using dot notation or the t.* syntax.
- C
The JSON files are not in the correct format for Athena.
Correct. JSON files may have timestamps in an unsupported format or structural issues preventing proper parsing.
- D
The 'timestamp' field is not defined as a partition column in the Glue table.
Why wrong: Incorrect. While partition pruning helps performance, filtering on a non-partition column still scans data and returns matching rows.
Question 269 of 1,755
MLS-C01 Athena data types Practice Question
This MLS-C01 practice question tests your understanding of data engineering. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: athena data types. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A data scientist is building a training dataset from data stored in Amazon S3. The data consists of JSON files each containing a 'timestamp' field. The scientist wants to use AWS Glue to catalog the data and enable querying via Amazon Athena. However, Athena queries are returning zero results for time-range filters. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
The JSON files are not in the correct format for Athena.
Athena supports querying JSON data, but the JSON files must have a schema that Athena can interpret. If the 'timestamp' field is in an unrecognized date/time format or the JSON structure is inconsistent, Athena may fail to parse the data correctly, resulting in zero rows for time-range filters. Option C is correct because the most likely cause is the JSON files not being in a format that Athena can parse properly for timestamp filtering. Option A is wrong because permission issues would cause an access denied error. Option B is wrong because Athena supports nested JSON. Option D is wrong because even if the timestamp is not a partition column, filtering on it should still return results if the data matches the filter condition.
Key principle: Athena data types
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The AWS Glue crawler does not have permissions to read the S3 bucket.
Why it's wrong here
Incorrect. Permission issues cause access denied errors, not zero results.
- ✗
Athena cannot query nested JSON objects.
Why it's wrong here
Incorrect. Athena can query nested JSON using dot notation or the t.* syntax.
- ✓
The JSON files are not in the correct format for Athena.
Why this is correct
Correct. JSON files may have timestamps in an unsupported format or structural issues preventing proper parsing.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Athena data types
- ✗
The 'timestamp' field is not defined as a partition column in the Glue table.
Why it's wrong here
Incorrect. While partition pruning helps performance, filtering on a non-partition column still scans data and returns matching rows.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates may assume that time-range filter failures are always due to missing partition columns, but often the issue is with the data format or timestamp parsing.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Athena data types
- JSON parsing in Athena
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Athena data types
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 |
What to study next
Got this wrong? Here's your next step.
Review athena data types, then practise related MLS-C01 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this MLS-C01 question test?
Data Engineering — This question tests Data Engineering — Athena data types.
What is the correct answer to this question?
The correct answer is: The JSON files are not in the correct format for Athena. — Athena supports querying JSON data, but the JSON files must have a schema that Athena can interpret. If the 'timestamp' field is in an unrecognized date/time format or the JSON structure is inconsistent, Athena may fail to parse the data correctly, resulting in zero rows for time-range filters. Option C is correct because the most likely cause is the JSON files not being in a format that Athena can parse properly for timestamp filtering. Option A is wrong because permission issues would cause an access denied error. Option B is wrong because Athena supports nested JSON. Option D is wrong because even if the timestamp is not a partition column, filtering on it should still return results if the data matches the filter condition.
What should I do if I get this MLS-C01 question wrong?
Review athena data types, then practise related MLS-C01 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Athena data types
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Last reviewed: Jun 20, 2026
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