The answer is to use Spot Instances for task nodes and configure the cluster to terminate after the job completes. Spot Instances offer up to a 90% discount over On-Demand pricing, and since task nodes are stateless and can be added or removed without affecting cluster stability, they are the ideal choice for cost reduction in EMR. Auto-termination ensures you are not paying for idle resources once the Spark pipeline finishes writing results back to S3. On the AWS Certified Data Engineer Associate DEA-C01 exam, this question tests your understanding of EMR cost optimization strategies, often appearing as a scenario where the cluster is underutilized. A common trap is selecting On-Demand core nodes for cost savings, but core nodes handle HDFS and should remain On-Demand for reliability. Memory tip: think “Spot for stateless tasks, auto-terminate to stop the clock.”
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 runs a data processing pipeline on Amazon EMR. The pipeline reads data from S3, processes it with Spark, and writes results back to S3. The engineer notices that the cluster is underutilized and wants to reduce costs. Which TWO actions should the engineer take? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Spot instances for task nodes.
Option A is correct because using Spot instances for task nodes in Amazon EMR can significantly reduce costs, as Spot instances are spare EC2 capacity offered at up to 90% discount compared to On-Demand instances. Since task nodes are stateless and can be added or removed without affecting cluster stability, they are ideal candidates for Spot instances, allowing the engineer to lower expenses while maintaining processing capacity.
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.
✓
Use Spot instances for task nodes.
Why this is correct
Spot instances are cheaper than On-Demand.
Related concept
Read the scenario before looking for a memorised answer.
✓
Configure the cluster to terminate after the job completes.
Why this is correct
Auto-termination avoids paying for idle resources.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the master node to a larger instance type.
Why it's wrong here
Larger master node increases cost.
✗
Enable EMRFS consistent view.
Why it's wrong here
Consistent view ensures data consistency but does not reduce cost.
✗
Increase the number of core nodes to improve parallelism.
Why it's wrong here
More nodes increase cost, not reduce.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse cost optimization features like Spot instances and auto-termination with performance improvements or data consistency settings, leading them to select options that increase resources or enable features unrelated to cost reduction.
Detailed technical explanation
How to think about this question
Spot instances can be interrupted with a two-minute termination notice, so they are best suited for fault-tolerant workloads like Spark processing where task nodes can be replaced or tasks retried. EMR automatically handles Spot instance interruptions by launching replacement instances or using a mixed instance policy, and you can configure a percentage of On-Demand instances as a fallback to ensure job completion. In practice, using Spot instances for task nodes can reduce costs by 50-90% depending on instance type and region, but requires careful tuning of Spark speculative execution and checkpointing to handle interruptions gracefully.
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.
TExam Day Tips
→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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Spot instances for task nodes. — Option A is correct because using Spot instances for task nodes in Amazon EMR can significantly reduce costs, as Spot instances are spare EC2 capacity offered at up to 90% discount compared to On-Demand instances. Since task nodes are stateless and can be added or removed without affecting cluster stability, they are ideal candidates for Spot instances, allowing the engineer to lower expenses while maintaining processing capacity.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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