DEA-C01 Data Store Management Practice Question
A data engineering team is using Amazon EMR to process large datasets stored in Amazon S3. The cluster uses Spot Instances for cost savings. During processing, the team notices that tasks are failing due to Spot Instance interruptions. The team needs to make the EMR job resilient to Spot interruptions without increasing costs significantly. Which solution should they implement?
⚠ Common exam trap
The trap is assuming that any mix of Spot and On-Demand is sufficient, but the allocation strategy and node type assignment are critical: using 'lowest price' or putting core nodes on Spot can lead to frequent job failures despite having On-Demand instances.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use EMR instance fleets with a mix of Spot and On-Demand, setting the allocation strategy to 'diversified' and using On-Demand for core nodes.
Using EMR instance fleets with a mix of Spot and On-Demand instances, setting the allocation strategy to 'diversified' and using On-Demand for core nodes, provides resilience against Spot interruptions while controlling costs. The 'diversified' strategy spreads Spot instances across multiple instance pools and Availability Zones, reducing the impact of a single Spot interruption. Core nodes, which handle HDFS data and run tasks, are kept on On-Demand to ensure stability, while task nodes can use Spot for cost savings.
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 EMR instance fleets with a mix of Spot and On-Demand, but set the allocation strategy to 'lowest price'.
Why it's wrong here
'Lowest price' allocation selects the cheapest Spot pools, which are the most heavily bid and therefore interrupted most often, worsening task failures. It is tempting because it minimises hourly cost, but capacity-optimised allocation, which picks pools with deepest available capacity, is what actually reduces interruptions.
- ✗
Increase the number of core nodes using On-Demand instances.
Why it's wrong here
Adding On-Demand core nodes removes Spot savings on that capacity and does not stop task failures on remaining Spot task nodes. It is tempting because On-Demand instances are never interrupted, but the stem requires resilience without significantly increasing costs, which this raises.
- ✗
Use only Spot Instances but enable automatic termination and checkpointing.
Why it's wrong here
Checkpointing preserves progress but does not prevent interruption; tasks still fail and the cluster loses capacity, and automatic termination ends the cluster entirely. It is tempting because checkpointing aids recovery, yet it addresses restart cost, not the resilience the stem requires without added expense.
- ✓
Use EMR instance fleets with a mix of Spot and On-Demand, setting the allocation strategy to 'diversified' and using On-Demand for core nodes.
Why this is correct
Instance fleets with a diversified allocation strategy spread Spot capacity across multiple instance types and Availability Zones, reducing simultaneous interruption risk, while On-Demand core nodes preserve HDFS and task durability. This keeps costs low without losing resilience.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.