The answer is to use a Lambda function to merge small files into larger ones before Glue processes them. This strategy directly addresses the root cause of poor performance: the overhead of reading millions of tiny files, each requiring a separate file open, metadata lookup, and task scheduling. By consolidating files into larger blocks—typically 128 MB or more—you reduce the number of read operations and allow Glue to process data in efficient, sequential scans. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Glue’s distributed architecture and the common pitfall of assuming more compute (DPUs) or S3 Select will solve I/O bottlenecks. A frequent trap is choosing “increase DPUs,” which adds cost but doesn’t fix the file-per-task overhead. Remember the memory tip: “Small files, big pain—merge before the train.”
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 company ingests millions of small files (1-10 KB) into Amazon S3 every hour. These files are then processed by AWS Glue ETL jobs. The Glue jobs are slow because of the overhead of reading many small files. Which strategy will most effectively improve Glue job performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a Lambda function to merge small files into larger ones before Glue processes them.
Grouping small files into larger ones (e.g., by merging in a preprocessing step) reduces the number of file read operations and improves Glue's efficiency. Using S3 Select or increasing DPUs helps but doesn't address the root cause.
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.
✗
Enable Glue job bookmark.
Why it's wrong here
Job bookmarks are for incremental processing, not for handling small file overhead.
✗
Increase the number of DPUs for the Glue job.
Why it's wrong here
More DPUs help parallelism but the overhead of opening many small files remains.
✗
Use S3 Select to filter data before Glue reads it.
Why it's wrong here
S3 Select can reduce data scanned but doesn't reduce the overhead of opening many small files.
✓
Use a Lambda function to merge small files into larger ones before Glue processes them.
Why this is correct
Merging files reduces the number of objects, speeding up Glue's list and read operations.
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 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: Use a Lambda function to merge small files into larger ones before Glue processes them. — Grouping small files into larger ones (e.g., by merging in a preprocessing step) reduces the number of file read operations and improves Glue's efficiency. Using S3 Select or increasing DPUs helps but doesn't address the root cause.
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.
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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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