AWS Certified SysOps Administrator – Associate — Question 427

A company is planning to host its stateful web-based applications on AWS. A SysOps administrator is using an Auto Scaling group of Amazon EC2 instances. The web applications will run 24 hours a day, 7 days a week throughout the year. The company must be able to change the instance type within the same instance family later in the year based on the traffic and usage patterns.
Which EC2 instance purchasing option will meet these requirements MOST cost-effectively?

Answer options

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

Correct answer: A

Explanation

Convertible Reserved Instances are the most cost-effective choice because they offer a significant discount for 24/7 workloads while allowing the modification of instance types within the same family. Standard Reserved Instances do not permit changing instance types, and Spot Instances are unsuitable because they can be terminated abruptly, which risks stateful application data. On-Demand Instances would satisfy the flexibility requirement but at a much higher cost than Reserved Instances.