The correct approach is to use Parquet format with Snappy compression and partition the data by year, month, and day. This combination directly optimizes Athena query performance by minimizing the amount of data scanned per query—partitioning prunes irrelevant directories, while the columnar Parquet format reads only the necessary columns, and Snappy compression reduces storage footprint without sacrificing speed. On the AWS Certified Data Engineer Associate DEA-C01 exam, this question tests your understanding of cost-effective data lake design, where the key principle is that Athena pricing is based on data scanned. A common trap is choosing a solution that compresses data but lacks partitioning, or one that creates many small files, which increases overhead. Remember the memory tip: “Partition to prune, Parquet to project, Snappy to shrink.”
DEA-C01 Data Store Management Practice Question
This DEA-C01 practice question tests your understanding of data store management. 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 in Parquet format, partitioned by date. The engineer needs to ensure that queries using Amazon Athena are cost-effective and perform well. Which approach should the engineer take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Parquet format with Snappy compression and partition by year, month, day.
Option C is correct because partitioning and columnar storage reduce data scanned. Option A increases cost due to many small files. Option B is less efficient than Parquet. Option D compresses but doesn't partition.
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 uncompressed CSV format and partition by year, month, day, hour.
Why it's wrong here
CSV is not columnar and scanning all columns increases cost.
✗
Use JSON format with Snappy compression and partition by date only.
Use Gzip-compressed CSV files with no partitioning.
Why it's wrong here
No partitioning forces full table scans.
✓
Use Parquet format with Snappy compression and partition by year, month, day.
Why this is correct
Parquet is columnar, reducing I/O, and partitioning limits 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 Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Parquet format with Snappy compression and partition by year, month, day. — Option C is correct because partitioning and columnar storage reduce data scanned. Option A increases cost due to many small files. Option B is less efficient than Parquet. Option D compresses but doesn't partition.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A data engineer is designing a data lake on Amazon S3. Data is ingested from multiple sources in JSON format. The engineer needs to optimize query performance for Amazon Athena while minimizing storage costs. Which storage strategy should the engineer use?
medium
A.Store data as CSV files in a single S3 bucket without prefixes.
✓ B.Convert data to Parquet format and partition by date.
C.Store data as JSON files in a single prefix without partitioning.
D.Store compressed JSON files in Amazon S3 Glacier.
Why B: Parquet is a columnar format that reduces storage size and improves query performance in Athena. Partitioning by date further optimizes queries that filter by date. Option B is correct. Option A: storing as raw JSON with no partitioning leads to higher costs and slower queries. Option C: using Glacier for hot data adds retrieval latency and is not suitable for frequent queries. Option D: storing in a single bucket with no structure causes full scans.
Variation 2. A data engineer is designing a data lake on Amazon S3. The data is partitioned by year, month, day, and hour. The engineer needs to ensure that queries using Amazon Athena are cost-effective and performant. The data is written in Parquet format, and the total volume is 50 TB. Which approach minimizes query costs?
hard
A.Use AWS Glue Data Catalog to catalog the data
B.Convert data to CSV format
✓ C.Partition the data by year, month, day, and hour
D.Use S3 Intelligent-Tiering storage class
Why C: Option C is correct because partitioning by year, month, day, and hour allows Athena to use partition pruning, reading only the relevant S3 prefixes instead of scanning the entire 50 TB dataset. This drastically reduces the amount of data scanned per query, which directly lowers query costs (Athena charges per TB scanned). The existing Parquet format further optimizes performance through columnar storage and compression.
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.