AWS Certified SysOps Administrator – Associate (legacy) — Question 21

An application running on Amazon EC2 allows users to launch batch jobs for data analysis. The jobs are run asynchronously, and the user is notified when they are complete. While multiple jobs can run concurrently, a user's request need not be fulfilled for up to 24 hours. To run a job, the application launches an additional EC2 instance that performs all the analytics calculations. A job takes between 75 and 110 minutes to complete and cannot be interrupted.
What is the MOST cost-effective way to run this workload?

Answer options

• A. Run the application on On-Demand EC2 instances. Run the jobs on Spot Instances with a specified duration.
• B. Run the application on Reserved Instance EC2 instances. Run the jobs on AWS Lambda.
• C. Run the application on On-Demand EC2 instances. Run the jobs on On-Demand EC2 instances.
• D. Run the application on Reserved Instance EC2 instances. Run the jobs on Spot Instances with a specified duration.

Correct answer: D

Explanation

Option D is the most cost-effective because it combines the lower cost of Reserved Instances for the stable application layer with the cheaper Spot Instances for the batch jobs, which can be interrupted and have flexibility in scheduling. Options A and C do not leverage the cost benefits of Reserved Instances for the application, while Option B incorrectly suggests using AWS Lambda, which is not suited for long-running jobs that take between 75 and 110 minutes.