This DEA-C01 practice question tests your understanding of data operations and support. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 engineer is troubleshooting a slow-running Amazon Athena query on a large dataset stored in S3. The query scans many small files. Which TWO actions can improve query performance?
Increase the number of files to increase parallelism
Why wrong: Too many files hurt performance.
Disable S3 server-side encryption
Why wrong: Encryption has minimal performance impact.
Concatenate small files into larger files
Reduces file open overhead.
Partition the data by a frequently filtered column
Limits data scanned.
Convert files from CSV to JSON
Why wrong: JSON is not more efficient than CSV.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Concatenate small files into larger files
Option A is correct because compacting small files into larger ones reduces overhead. Option C is correct because partitioning limits data scanned. Option B is wrong because converting to Parquet helps but is not one of the two selected here (though it is also good). Option D is wrong because more files increase overhead. Option E is wrong because disabling encryption does not affect performance.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Increase the number of files to increase parallelism
Why it's wrong here
Too many files hurt performance.
Disable S3 server-side encryption
Why it's wrong here
Encryption has minimal performance impact.
Concatenate small files into larger files
Why this is correct
Reduces file open overhead.
Related concept
Static NAT maps one inside address to one outside address.
Partition the data by a frequently filtered column
Why this is correct
Limits data scanned.
Related concept
Static NAT maps one inside address to one outside address.
Convert files from CSV to JSON
Why it's wrong here
JSON is not more efficient than CSV.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
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.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
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FAQ
Data Operations and Support — This question tests Data Operations and Support — Static NAT maps one inside address to one outside address..
The correct answer is: Concatenate small files into larger files — Option A is correct because compacting small files into larger ones reduces overhead. Option C is correct because partitioning limits data scanned. Option B is wrong because converting to Parquet helps but is not one of the two selected here (though it is also good). Option D is wrong because more files increase overhead. Option E is wrong because disabling encryption does not affect performance.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 20, 2026
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.
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