How can the user configure this?

A user has setup Auto Scaling with ELB on the EC2 instances. The user wants to configure that whenever the CPU utilization is below 10%, Auto Scaling should remove one instance.

How can the user configure this?
A . The user can get an email using SNS when the CPU utilization is less than 10%. The user can use the desired capacity of Auto Scaling to remove the instance
B . Use CloudWatch to monitor the data and Auto Scaling to remove the instances using scheduled actions
C . Configure CloudWatch to send a notification to Auto Scaling Launch configuration when the CPU utilization is less than 10% and configure the Auto Scaling policy to remove the instance
D . Configure CloudWatch to send a notification to the Auto Scaling group when the CPU Utilization is less than 10% and configure the Auto Scaling policy to remove the instance

View Answer

Answer: D

Explanation:

Amazon CloudWatch alarms watch a single metric over a time period that the user specifies and performs one or more actions based on the value of the metric relative to a given threshold over a number of time periods. The user can setup to receive a notification on the Auto Scaling group with the CloudWatch alarm when the CPU utilization is below a certain threshold. The user can configure the Auto Scaling policy to take action for removing the instance. When the CPU utilization is below 10% CloudWatch will send an alarm to the Auto Scaling group to execute the policy.