DOP-C02 Resilient Cloud Solutions Practice Question
A company runs a critical batch processing workload on Amazon EMR that must complete within a 2-hour window each night. The workload is fault-tolerant but must be resilient to instance failures. Currently, the EMR cluster uses instance fleets with Spot Instances. Recently, Spot Instance interruptions caused the cluster to take over 3 hours to complete. Which change will MOST effectively ensure the workload completes within the 2-hour window despite Spot interruptions?
⚠ Common exam trap
Test-takers frequently assume increasing parallelism (Option A) or using On-Demand instances (Option B) are the only ways to handle Spot interruptions, overlooking the cost-effective and resilient design of mixed instances across zones.
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 a mixed instances policy that includes multiple instance types across different Availability Zones.
A mixed instances policy across multiple Availability Zones increases the diversity of Spot capacity pools. When one instance type or zone experiences interruptions, the cluster can fall back to other pools, reducing the likelihood of prolonged delays. This approach directly addresses Spot interruption risk without sacrificing cost efficiency, as On-Demand instances would.
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 core nodes to 20 to improve parallelism.
Why it's wrong here
Increasing the number of core nodes to 20 improves parallelism but does not address the root cause of Spot interruptions. Spot capacity is reclaimed independently of node count; more nodes actually increase the surface area for potential interruption. A larger fleet without a diversified instance strategy or AZ spread remains equally vulnerable to simultaneous capacity reclamation.
- ✗
Switch to using On-Demand instances for all nodes.
Why it's wrong here
Switching all nodes to On-Demand guarantees that interruptions will not occur, but it defeats the purpose of using Spot and significantly increases costs. The question focuses on mitigating interruptions while arguably maintaining cost efficiency, so a wholesale switch is an over-correction. It also does not leverage the resilience benefits of diversifying instance types and Availability Zones that a mixed policy provides.
- ✓
Use a mixed instances policy that includes multiple instance types across different Availability Zones.
Why this is correct
Using a mixed instances policy with multiple instance types across different Availability Zones is the recommended way to reduce Spot interruption risk in EMR. This approach makes the cluster's Spot capacity pool more diverse, so a capacity reclamation event in one pool is unlikely to affect all nodes simultaneously. EMR's instance fleets can automatically provision from the specified pools, improving both initial capacity acquisition and fault tolerance during interruptions.
- ✗
Configure the cluster to terminate idle nodes after 5 minutes to reduce costs.
Why it's wrong here
Configuring the cluster to terminate idle nodes after 5 minutes is a cost-control measure that has no bearing on Spot interruptions. It may even harm a batch workload by shutting down nodes during brief processing gaps, causing reconfiguration overhead. This action does not alter the instance type or AZ diversity of the fleet, so the risk of interruption remains unchanged.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-C02 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 DOP-C02 exam.