Which solution meets these requirements MOST cost-effectively?
Stop the DB instance when tests are completed. Restart the DB instance when required.
Use an Auto Scaling policy with the DB instance to automatically scale when tests are completed.
Create a snapshot when tests are completed. Terminate the DB instance and restore the snapshot when required.
Modify the DB instance to a low-capacity instance when tests are completed. Modify the DB instance again when required.
Explanations:
Stopping an RDS instance is only possible for up to 7 days at a time. This option would not work effectively for a monthly process.
Amazon RDS does not support Auto Scaling directly on DB instances; scaling is managed manually or with specific configurations.
Creating a snapshot and terminating the instance reduces monthly costs. Restoring the snapshot recreates the instance only when needed, saving costs effectively.
Modifying the instance type frequently would cause downtime and additional configuration effort, which is less cost-effective and practical.
I rank that the answer is:
Create a snapshot when tests are completed. Terminate the DB instance and restore the snapshot when required.