SAA-C03 Design Cost-Optimized Architectures Practice Question
A data analytics team runs an Amazon EMR cluster for 2 hours every weekday morning to process a daily batch. The cluster must be fully available during that window, and the team wants the lowest possible compute cost. The jobs are stateless and can be re-run if a node fails. Which configuration should a solutions architect recommend?
⚠ Common exam trap
The trap here is assuming any long-running or recurring workload automatically benefits from Reserved Instances, when short daily batch jobs are better served by Spot for fault-tolerant task nodes.
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
✓
Provision the EMR cluster with On-Demand Instances for the master node and Spot Instances for task nodes.
The workload is a short, recurring, fault-tolerant batch job, so the best cost strategy is to combine a stable On-Demand master with Spot task nodes that can be reclaimed and restarted. This preserves cluster availability while taking advantage of Spot's lower pricing. Long-term commitments and Dedicated Hosts are poor fits because the compute is neither continuous nor compliance-driven.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Provision the EMR cluster entirely with Dedicated Hosts to guarantee physical isolation and predictable pricing.
Why it's wrong here
Dedicated Hosts are intended for licensing and compliance requirements, not for reducing cost on a short daily batch. They are more expensive than On-Demand or Spot and do not provide interruption tolerance. For a 2-hour stateless EMR job, this choice increases cost without addressing the workload's fault tolerance.
- ✓
Provision the EMR cluster with On-Demand Instances for the master node and Spot Instances for task nodes.
Why this is correct
Using On-Demand for the master node keeps the cluster's control plane stable, while Spot Instances on task nodes can reduce compute cost because the stateless batch jobs can be re-run if a Spot node is reclaimed. This matches the SAA-C03 cost-optimization goal for transient, fault-tolerant analytics workloads.
- ✗
Provision the EMR cluster with On-Demand Instances for all node types and enable automatic scaling.
Why it's wrong here
Automatic scaling helps match capacity to demand, but using On-Demand for every node ignores the significant savings available from Spot for task nodes. Since the jobs are stateless and can be re-run, On-Demand everywhere is unnecessarily expensive for this short, interruption-tolerant batch workload.
- ✗
Provision the EMR cluster with Reserved Instances for a 3-year term to lock in the lowest hourly rate.
Why it's wrong here
Reserved Instances require a long-term commitment and are cost-effective only for steady, predictable usage. A 2-hour daily batch does not justify a 3-year reservation, and the cluster is not running continuously. This option would waste money on unused reserved capacity rather than optimizing the transient compute cost.
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Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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