The correct answer is to enable the 'Group small files' setting in the Glue job or use a DynamicFrame with coalesce. This optimization directly addresses the performance bottleneck caused by thousands of tiny source files, as each file triggers overhead for task scheduling and metadata operations. By grouping these small files into fewer, larger partitions, AWS Glue reduces the number of tasks and improves read throughput, making the transformation to Parquet far more efficient. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Glue job tuning for real-world data lakes, where small file proliferation is a common trap—many candidates mistakenly increase DPUs, but that only adds compute power without fixing the I/O overhead. A useful memory tip is to think of "glue small files optimization" as the "fewer, fatter" principle: fewer partitions with fatter files always outperform many tiny ones in distributed processing.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. 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. 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 needs to transform JSON data from Amazon S3 into Parquet format using AWS Glue. The source files are in a bucket with thousands of small files. What is the best practice to optimize the Glue job performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable 'Group small files' in the Glue job or use a DynamicFrame with coalesce.
Grouping small files into fewer partitions reduces overhead. Option A is correct. Option B is wrong because increasing DPUs may not help with small files. Option C is wrong because converting to CSV adds extra step. Option D is wrong because Parquet is more efficient for Glue.
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.
✗
Convert the JSON files to CSV before processing with Glue.
Why it's wrong here
CSV is less efficient; Parquet is better.
✓
Enable 'Group small files' in the Glue job or use a DynamicFrame with coalesce.
Why this is correct
Grouping reduces the number of tasks and improves performance.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use an AWS Lambda function to pre-process the files.
Why it's wrong here
Lambda adds complexity and cost.
✗
Increase the number of DPUs to the maximum.
Why it's wrong here
Small files cause overhead regardless of DPUs.
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 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
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 Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable 'Group small files' in the Glue job or use a DynamicFrame with coalesce. — Grouping small files into fewer partitions reduces overhead. Option A is correct. Option B is wrong because increasing DPUs may not help with small files. Option C is wrong because converting to CSV adds extra step. Option D is wrong because Parquet is more efficient for Glue.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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
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