The answer is to change the core node instance type to r5.xlarge because memory-optimized instances directly address the root cause of the EMR Spark OutOfMemoryError. When processing large Parquet datasets in Spark SQL, each executor needs sufficient RAM to hold shuffle data and perform transformations; the r5.xlarge provides more memory per core than the general-purpose m5.xlarge, preventing the JVM from exhausting its heap. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding that EMR Spark OOM memory optimization often requires scaling memory vertically rather than increasing parallelism or cores, which can actually worsen resource contention. A common trap is assuming more partitions or executor cores will fix memory pressure, but without additional RAM, those changes only fragment the available heap further. Remember the memory tip: when Spark tasks fail with OOM, think “more RAM, not more tasks” — the r in r5 stands for RAM-optimized.
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 Amazon EMR to process large datasets stored in Amazon S3. The data is in Parquet format and partitioned by date. The EMR cluster uses Spark SQL for transformations. Recently, the job has been slow and some tasks are failing due to 'java.lang.OutOfMemoryError'. The cluster has 10 core nodes of type m5.xlarge. Which configuration change would MOST improve performance and stability?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the core node instance type to r5.xlarge (memory-optimized).
Option A is correct because using a memory-optimized instance type like r5.xlarge provides more memory per core. Option B is wrong because more partitions with same resources can cause overhead. Option C is wrong because increasing executor cores without increasing memory can worsen memory issues. Option D is wrong because Kryo serialization reduces memory for serialized objects, not OOM from processing.
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 Spark partitions using repartition(), but keep the same nodes.
Why it's wrong here
May increase parallelism but not memory per task.
✓
Change the core node instance type to r5.xlarge (memory-optimized).
Why this is correct
More memory per node helps OOM.
Related concept
Read the scenario before looking for a memorised answer.
✗
Increase the number of executor cores in the Spark configuration.
Why it's wrong here
Would increase parallelism but not memory per core.
✗
Enable Kryo serialization in the Spark configuration.
Why it's wrong here
Reduces serialization overhead but not OOM.
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: Change the core node instance type to r5.xlarge (memory-optimized). — Option A is correct because using a memory-optimized instance type like r5.xlarge provides more memory per core. Option B is wrong because more partitions with same resources can cause overhead. Option C is wrong because increasing executor cores without increasing memory can worsen memory issues. Option D is wrong because Kryo serialization reduces memory for serialized objects, not OOM from processing.
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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