SAA-C03 Design Cost-Optimized Architectures Practice Question
A solutions architect is designing a system for batch processing of large image files. The process can be interrupted and resumed later without loss of data. The workload is expected to run for several hours each night. Which EC2 instance purchasing option will provide the lowest cost?
⚠ Common exam trap
Candidates frequently choose Reserved Instances. While they provide savings, they are for steady-state workloads, not interruptible batch processing, and do not offer the deepest discounts possible compared to Spot.
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
✓
Spot Instances
Spot Instances offer the deepest discounts (up to 90%) on EC2 capacity. They are ideal for fault-tolerant, flexible, and interruptible workloads like batch processing. Since the application can handle interruptions and resume progress, the risk of AWS reclaiming the capacity is offset by the massive cost savings compared to On-Demand or Reserved Instances.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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On-Demand Instances
Why it's wrong here
On-Demand instances are the most expensive way to consume EC2 capacity because you pay for flexibility without any long-term commitment. For a workload that runs every night and can handle interruptions, paying the full hourly rate is unnecessary and results in significantly higher costs than using spare AWS capacity.
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Dedicated Hosts
Why it's wrong here
Dedicated Hosts are physical servers dedicated to a single customer, usually required for specific compliance needs or complex licensing models (BYOL). They are much more expensive than standard multi-tenant EC2 instances and offer no benefit for a simple batch processing workload that can run on shared infrastructure.
- ✓
Spot Instances
Why this is correct
Spot Instances allow you to bid on spare AWS capacity at a fraction of the On-Demand price. Because the batch processing job is interruptible and can resume, it is the perfect use case for Spot. If AWS needs the capacity back, the instance is terminated, but the cost savings remain substantial.
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Reserved Instances
Why it's wrong here
Reserved Instances require a 1-year or 3-year commitment and are best suited for steady-state workloads that run continuously. While they offer a discount over On-Demand, they do not provide the same level of savings as Spot Instances for workloads that are only active for a few hours per night.
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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.