AWS Certified Cloud Practitioner — Question 660

A company has developed a distributed application that recovers gracefully from Interruptions. The application periodically processes large volumes of data by using multiple Amazon EC2 Instances. The application is sometimes idle for months.

Which EC2 instance purchasing option is MOST cost-effective for this use case?

Answer options

• A. Reserved Instances
• B. Spot Instances
• C. Dedicated Instances
• D. On-Demand Instances

Correct answer: B

Explanation

Spot Instances are the most cost-effective choice because they utilize spare EC2 capacity at significant discounts, which perfectly suits workloads that are interruption-tolerant and run intermittently. Reserved Instances are not cost-effective here because they require a continuous financial commitment even when the application is idle for months. On-Demand Instances are more expensive than Spot Instances, and Dedicated Instances incur unnecessary premium costs for physical isolation that is not required.