SAA-C03 Design Cost-Optimized Architectures Practice Question
A small e-commerce company hosts its website on a single EC2 instance in a public subnet. The site receives low but steady traffic. The company wants to reduce cost and is willing to accept a brief interruption if the instance is terminated. The workload can be restarted automatically. Which EC2 purchasing option should the company use to minimize cost?
⚠ Common exam trap
The trap here is assuming that a steady workload always requires a commitment-based purchase, when interruptible workloads can use Spot for maximum savings.
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 provide the deepest discounts and are designed for workloads that can tolerate interruptions. Since the company accepts a brief interruption and can restart automatically, Spot aligns perfectly with the workload characteristics. On-Demand, Reserved Instances, and Dedicated Hosts are either more expensive or require commitments that are unnecessary for this flexible, low-traffic website.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
On-Demand Instances
Why it's wrong here
On-Demand Instances provide flexibility and no long-term commitment, but they are priced higher than other options. For a steady, low-traffic website that can tolerate interruption and restart automatically, a lower-cost option exists. On-Demand is best for workloads that cannot be interrupted or have unpredictable usage, but here the company explicitly accepts brief interruptions, so On-Demand is not the most cost-effective choice.
- ✓
Spot Instances
Why this is correct
Spot Instances offer the largest discounts, up to 90% off On-Demand prices, and are ideal for workloads that can tolerate interruption. The company accepts a brief interruption and can restart the instance automatically, which aligns with Spot behavior. For a low-traffic website with steady usage, Spot can significantly reduce cost. Using a Spot Fleet or Auto Scaling group with a diversified allocation strategy improves availability.
- ✗
Reserved Instances with a 3-year term and all upfront payment
Why it's wrong here
Reserved Instances provide a significant discount in exchange for a commitment to a specific instance family and Region for the term. However, they require a long-term commitment and upfront payment, which may not be suitable for a small company with uncertain future needs. Additionally, the company is willing to accept interruptions, so a commitment-based option is not necessary and may not be the most cost-effective given the flexibility offered by Spot.
- ✗
Dedicated Hosts
Why it's wrong here
Dedicated Hosts provide physical servers dedicated to your use, which is the most expensive option and is typically used for licensing or compliance requirements. For a small e-commerce site with low traffic that can tolerate interruptions, Dedicated Hosts are unnecessary and far more costly than other options. They do not align with the goal of minimizing cost for a simple, restartable workload.
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Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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