The answer is partitioning input data by date and enabling partition pruning in the AWS Glue job. This is the most effective action because partition pruning allows Glue to read only the relevant subdirectories (e.g., year/month/day) rather than scanning the entire S3 data lake, drastically reducing the volume of data processed and thereby cutting runtime. On the AWS Certified Data Engineer Associate DEA-C01 exam, this question tests your understanding of how data layout directly impacts ETL performance—a common trap is to focus on compute resources like DPUs or file formats, but the core principle is that minimizing data scanned yields the greatest efficiency gains. Remember, Parquet already provides compression and columnar storage, so the bottleneck here is the sheer volume of data read, not the format. Memory tip: “Prune the path, not the power” — always optimize data organization before scaling resources.
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 uses AWS Glue ETL jobs to process data from an S3 data lake. The job reads data in CSV format, transforms it, and writes to Parquet. The job runs daily and takes 2 hours to complete. The data volume is increasing by 20% each month. The engineer wants to reduce the job runtime. Which action is most effective?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Partition the input data in S3 by date and use partition pruning in the job
Option B is correct because partitioning data by date (e.g., year/month/day) allows Glue to read only the new partitions incrementally, reducing data scanned. Option A (increasing DPUs) may help but not as much as reducing data volume. Option C (using Spark) is already used by Glue. Option D (compression) is already Parquet, which is compressed.
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.
✗
Increase the number of DPUs for the Glue job
Why it's wrong here
More DPUs can speed up processing but linearly; partitioning reduces data volume.
✗
Enable compression on the input CSV files
Why it's wrong here
CSV compression reduces size but not as effective as partitioning; output is already Parquet.
✗
Switch from Python Shell to Spark ETL
Why it's wrong here
Glue ETL already uses Spark; Python Shell is for simpler jobs.
✓
Partition the input data in S3 by date and use partition pruning in the job
Why this is correct
Partition pruning limits the data read to only relevant partitions, drastically reducing processing time.
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.
Trap categories for this question
Command / output trap
CSV compression reduces size but not as effective as partitioning; output is already Parquet.
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: Partition the input data in S3 by date and use partition pruning in the job — Option B is correct because partitioning data by date (e.g., year/month/day) allows Glue to read only the new partitions incrementally, reducing data scanned. Option A (increasing DPUs) may help but not as much as reducing data volume. Option C (using Spark) is already used by Glue. Option D (compression) is already Parquet, which is compressed.
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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