SAA-C03 Design Cost-Optimized Architectures Practice Question
A financial analytics team runs a nightly Monte Carlo simulation on a cluster of Amazon EC2 instances. The simulation writes checkpoint files to an Amazon EBS volume, and the job can be safely restarted from the last checkpoint if interrupted. The team needs the lowest possible compute cost and can tolerate interruptions. The job must run every night and finish within a 6-hour window. Which solution meets these requirements MOST cost-effectively?
⚠ Common exam trap
The trap here is assuming that Reserved Instances are always the cheapest option for recurring workloads, ignoring that the workload is not running 24/7 and can tolerate interruptions.
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 Spot Instances with a persistent request and checkpointing to EBS.
Spot Instances are the most cost-effective choice for fault-tolerant, interruptible workloads, offering steep discounts over On-Demand. Because the simulation can resume from checkpoints, Spot interruptions are acceptable. A persistent Spot request helps maintain capacity to complete the job within the nightly window, while checkpointing to EBS preserves progress. Other purchasing options either cost more or do not suit the interruptible pattern.
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 On-Demand EC2 instances with a placement group for low-latency networking.
Why it's wrong here
On-Demand instances provide no cost savings for interruptible workloads and are significantly more expensive than other purchasing options. A placement group improves network performance but does not reduce compute cost. The simulation can tolerate interruptions, so paying full On-Demand rates is unnecessary and fails to meet the lowest-cost requirement.
- ✗
Use Dedicated Hosts to ensure physical isolation for the simulation.
Why it's wrong here
Dedicated Hosts are the most expensive EC2 option and are intended for licensing or compliance needs, not cost optimization. They do not provide any discount for interruptible workloads and would drastically increase the cost of the nightly simulation. Physical isolation is not required by the scenario, making this option inappropriate.
- ✗
Purchase a 1-year Standard Reserved Instance for each instance in the cluster.
Why it's wrong here
Reserved Instances provide discounts for steady-state usage but require a long-term commitment and assume the instances run continuously. This simulation runs only nightly, so Reserved Instances would be paid for during idle hours, increasing cost. They also do not address the interruptible nature of the job as cost-effectively as Spot.
- ✓
Use Spot Instances with a persistent request and checkpointing to EBS.
Why this is correct
Spot Instances offer up to 90% discounts compared to On-Demand and are ideal for fault-tolerant, interruptible workloads like this simulation. Checkpointing to EBS allows the job to resume after a Spot interruption. A persistent Spot request maintains the desired capacity, helping the job finish within the nightly window while minimizing compute cost.
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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 SAA-C03 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 SAA-C03 exam.