AWS Certified SysOps Administrator – Associate (legacy) — Question 660

A company wants to reduce costs on jobs that can be completed at any time. The jobs are currently run using multiple On-Demand Instances, and the jobs take just under 2 hours to complete. If a job fails for any reason, it can be restarted from the beginning.
Which method is the MOST cost-effective based on these requirements?

Answer options

• A. Purchase Reserved Instances to be used for job execution.
• B. Submit a request for a one-time Spot Instance for job execution.
• C. Submit a request for a Spot block to be used for job execution.
• D. Use a mixture of On-Demand and Spot Instances for job execution.

Correct answer: C

Explanation

A Spot block allows you to request Spot Instances with a continuous, guaranteed run time of 1 to 6 hours, making it the most cost-effective choice for a job taking just under 2 hours without risk of interruption. Standard Spot Instances are cheaper but can be interrupted at any time, which would force the 2-hour job to restart from the beginning. Reserved Instances and mixed On-Demand/Spot fleets are less cost-effective for short, flexible workloads that do not run continuously.