The correct answer is to implement partitioning, use columnar formats like Apache Parquet or ORC, and apply compression. These three actions directly optimize Amazon Athena query performance and reduce costs by minimizing the amount of data scanned per query. Partitioning prunes irrelevant data at the folder level, columnar formats read only the necessary columns, and compression shrinks storage footprint while keeping data queryable. On the AWS Certified Data Engineer Associate DEA-C01 exam, this concept tests your understanding of data lake optimization trade-offs—a common trap is confusing file count optimization with partitioning, or assuming S3 Select replaces Athena. Remember the memory tip: “Partition, Columnar, Compress” to cut cost and impress.
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 designing a data lake on Amazon S3. The data is ingested from multiple sources and must be queryable using Amazon Athena. The engineer needs to optimize query performance and reduce costs. Which THREE actions would achieve this?
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 by a commonly used filter column.
Option A: Partitioning reduces data scanned. Option C: Using columnar formats like Parquet reduces data scanned. Option E: Compression reduces storage and data scanned. Option B is wrong because the number of files should be optimized, not increased. Option D is wrong because S3 Select is for filtering within a single file, not for Athena.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Store data in many small files to increase parallelism.
Why it's wrong here
Many small files increase overhead and Athena charges per query.
✓
Partition the data by a commonly used filter column.
Why this is correct
Partition pruning limits the data scanned.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use S3 Select instead of Athena for queries.
Why it's wrong here
S3 Select is not a replacement for Athena; it's a different service.
✓
Compress data with a splittable compression format like Snappy.
Why this is correct
Compression reduces storage and I/O.
Related concept
Read the scenario before looking for a memorised answer.
✓
Convert data to Apache Parquet or ORC format.
Why this is correct
Columnar formats reduce data scanned.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Partition the data by a commonly used filter column. — Option A: Partitioning reduces data scanned. Option C: Using columnar formats like Parquet reduces data scanned. Option E: Compression reduces storage and data scanned. Option B is wrong because the number of files should be optimized, not increased. Option D is wrong because S3 Select is for filtering within a single file, not for Athena.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.