The answer is to increase the number of DPUs for the Glue job. This is correct because AWS Glue’s Apache Spark runtime distributes data across workers, and adding more DPUs increases the total cluster memory available for the shuffle and join phases of processing large datasets. When joining two datasets that are each hundreds of gigabytes, the default DPU allocation often provides insufficient memory for the in-memory hash join, causing an out-of-memory error. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Glue’s resource scaling and the relationship between DPU count and memory capacity. A common trap is to assume that increasing worker type (e.g., G.2X) alone fixes the issue, but for large joins, adding more workers (DPUs) is typically more effective because it increases parallelism and total heap space. Memory tip: think “More DPUs = More Memory for Joins” to recall that scaling horizontally resolves OOM errors on large dataset joins.
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 to transform data in an S3 data lake. The transformation logic requires joining two large datasets that are each hundreds of gigabytes. The Glue job runs out of memory. Which configuration change will most likely resolve this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the number of DPUs for the Glue job.
Increasing the number of DPUs provides more memory for the join operation. Glue automatically distributes data across workers, so more workers mean more total memory.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Repartition the data before the join.
Why it's wrong here
Repartitioning can help with skew but not necessarily with memory for a large join.
✓
Increase the number of DPUs for the Glue job.
Why this is correct
More DPUs provide more memory and parallelism, helping the join fit in memory.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Use a different file format like Parquet with compression.
Why it's wrong here
File format affects read efficiency but not join memory directly.
✗
Use the 'spark.sql.autoBroadcastJoinThreshold' setting to broadcast the smaller table.
Why it's wrong here
This helps if one table is small; both are large, so broadcasting won't help.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Increase the number of DPUs for the Glue job. — Increasing the number of DPUs provides more memory for the join operation. Glue automatically distributes data across workers, so more workers mean more total memory.
What should I do if I get this DEA-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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 retail company uses AWS Glue to process daily sales data from multiple CSV files stored in Amazon S3. The Glue job runs a PySpark script that reads the files, performs joins, and writes the output as Parquet. Recently, the job has been failing with 'Out of Memory' errors. The data volume has grown from 10 GB to 50 GB per day. The Glue job uses 10 DPUs and the standard worker type. The data engineer needs to fix the job without rewriting the script. What should the data engineer do?
medium
A.Split the input CSV files into smaller partitions.
B.Change the worker type to G.2X to get more memory per worker.
C.Decrease the number of DPUs to reduce memory contention.
✓ D.Increase the number of DPUs for the Glue job to 20.
Why D: Option C is correct. Increasing the number of DPUs provides more memory and compute resources, addressing the OOM error. Option A is wrong because changing worker type to G.2X may not be sufficient if the issue is simply memory; but increasing DPUs is a direct solution. Option B is wrong because splitting files does not reduce the memory needed for joins. Option D is wrong because decreasing DPUs would make the problem worse.
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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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