The correct actions are to enable Instance Fleets for diversified Spot instance types and to use a task instance group with Spot Instances for non-critical processing tasks. Instance Fleets reduce the risk of Spot interruptions by allowing EMR to automatically select from multiple instance types across different Availability Zones, while task instance groups isolate Spot-based workloads so that only non-essential tasks are lost if instances are reclaimed, preserving core node stability and HDFS data. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of EMR cost optimization with Spot Instances, a common topic where the trap is confusing core nodes (which store data) with task nodes (which are stateless). A useful memory tip is “Task for Temp, Core for Keep” — task nodes handle interruptible work, core nodes must stay persistent to avoid data loss.
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 data engineer is using Amazon EMR to process large datasets. The cluster uses a mix of Spot Instances and On-Demand Instances. The engineer wants to reduce costs while ensuring the job can complete even if Spot Instances are reclaimed. 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
✓
Enable Instance Fleets to use multiple instance types for Spot Instances.
Option A is correct because enabling Instance Fleets allows EMR to diversify instance types for Spot, reducing the chance of interruption. Option D is correct because using a task instance group with Spot instances for non-critical tasks ensures that only those tasks are interrupted. Option B is incorrect because using only On-Demand increases cost. Option C is incorrect because reducing core nodes may cause data loss if Spot nodes storing HDFS are reclaimed. Option E is incorrect because enabling termination protection is for accidental termination, not Spot interruptions.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 Instance Fleets to use multiple instance types for Spot Instances.
Why this is correct
Instance Fleets reduce the impact of Spot interruptions by diversifying instance types.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use only On-Demand Instances for all nodes.
Why it's wrong here
This increases cost, not reduces.
✗
Use Spot Instances for core nodes to reduce cost.
Why it's wrong here
Core nodes hold HDFS data; Spot interruptions can cause data loss.
✗
Enable termination protection for the cluster.
Why it's wrong here
Termination protection prevents accidental termination, not Spot interruptions.
✓
Use a task instance group with Spot Instances for non-critical processing tasks.
Why this is correct
Task nodes are ephemeral and do not store data; they are ideal for Spot.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
Data Operations and Support — This question tests Data Operations and Support — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Enable Instance Fleets to use multiple instance types for Spot Instances. — Option A is correct because enabling Instance Fleets allows EMR to diversify instance types for Spot, reducing the chance of interruption. Option D is correct because using a task instance group with Spot instances for non-critical tasks ensures that only those tasks are interrupted. Option B is incorrect because using only On-Demand increases cost. Option C is incorrect because reducing core nodes may cause data loss if Spot nodes storing HDFS are reclaimed. Option E is incorrect because enabling termination protection is for accidental termination, not Spot interruptions.
What should I do if I get this DEA-C01 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DEA-C01 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Variation 1. A company uses Amazon EMR to run Spark jobs on a transient cluster. The jobs process data from S3 and write results back to S3. The team wants to reduce costs by optimizing the cluster. Which action should the team take?
easy
✓ A.Use Spot Instances for the task nodes.
B.Increase the number of core nodes and use larger instance types.
C.Enable EMRFS consistent view.
D.Terminate the cluster after each job and manually restart it for the next job.
Why A: Using Spot Instances for task nodes in a transient EMR cluster significantly reduces compute costs because Spot Instances are spare AWS EC2 capacity offered at up to 90% discount compared to On-Demand. Since transient clusters are terminated after job completion, the risk of Spot Instance interruptions is mitigated—the job can simply be retried on a new cluster if needed. This directly addresses the cost optimization goal without sacrificing job functionality.
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Question Discussion
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