An application includes an Autoscaling Group. It has been determined that the best way to scale the group is based on the number of concurrent users. How can you achieve this?

Answer options:

A.Create a tag for the Group to contain the number of concurrent users.
B.Create a custom metric for the number of concurrent users.
C.Since concurrent user metrics are not available, base the scaling of the group on CPU percentage.
D.Since concurrent user metrics are not available, base the scaling of the group on Memory percentage.

Answer – B
The AWS Documentation mentions the following.
With target tracking scaling policies, you select a predefined metric or configure a customized metric and set a target value. Application Auto Scaling creates and manages the CloudWatch alarms that trigger the scaling policy and calculates the scaling adjustment based on the metric and the target value. The scaling policy adds or removes capacity as required to keep the metric at, or close to, the specified target value. In addition to keeping the metric close to the target value, a target tracking scaling policy also adjusts to changes in the metric due to a changing load pattern. It minimizes changes to the capacity of the scalable target.
Since you can define a custom metric based on concurrent usage, you can scale the Autoscaling group based on that. Based on this, all other options are invalid.
For more information on auto-scaling based on target tracking, please refer to the below URL-
https://docs.aws.amazon.com/autoscaling/application/userguide/application-auto-scaling-target-tracking.html