You have a distributed application that periodically processes large volumes of data across multiple Amazon EC2 Instances. The application is designed to recover gracefully from Amazon EC2 instance failures. You are required to accomplish this task most cost-effectively.
Which of the following will meet your requirements?
 

Answer options:

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

Answer - A
When you think of cost effectiveness, you can either have to choose Spot or Reserved instances. Now when you have a regular processing job, the best is to use spot instances. Since your application is designed to recover gracefully from Amazon EC2 instance failures, there is no issue even if you lose the Spot instances.
For more information on spot instances, please visit the URL:
https://aws.amazon.com/ec2/spot/