Your application’s Auto Scaling Group scales up too much and stays scaled up even when traffic decreases. What should you do to fix this?

Answer options:

A.Set a longer cooldown period on the Group, so the system stops overshooting the target capacity. The issue is that the scaling system doesn’t allow enough time for new instances to begin servicing requests before measuring aggregate load again.
B.Calculate the bottleneck or constraint on the compute layer, select that as the new metric, and set the CloudWatch metric thresholds to the bounding values that begin to affect response latency.
C.Raise the CloudWatch Alarms threshold associated with your autoscaling group, so the scaling takes more of an increase in demand before beginning.
D.Use larger instances instead of lots of smaller ones, so the Group stops scaling out so much and wasting resources at the OS level, since the OS uses a higher proportion of resources on smaller instances.

Answer – B
The major problem is that the right metric is not being used for the auto-scaling activities.
Option A is not valid because as the metric is still wrong, even if the cooldown timer is enlarged, the ASG may still keep scaling up when traffic is decreasing.
Option C is not valid because increasing the Cloudwatch alarm metric will not ensure that the instances scale down when the traffic decreases.
Option D is not valid because the question does not mention any constraints that point to the instance size.
For an example of using custom metrics for scaling in and out, please follow the below link for a use case.
https://blog.powerupcloud.com/aws-autoscaling-based-on-database-query-custom-metrics-f396c16e5e6a