You have an application hosted on AWS consisting of EC2 Instances launched via an Auto Scaling Group. You notice that the EC2 Instances are not scaling when the traffic is high. Which check should be done to ensure that the scaling occurs as expected?

Answer options:

A.Ensure that the right metrics are being used to trigger the scaling.
B.Check your scaling policies to see whether more than one policy is triggered by an event.
C.Ensure that AutoScaling health checks are being used.
D.Ensure that you are using Load Balancers.

Correct Answer – A
There could be several reasons mentioned in AWS Documentation. But only options A and B are applicable from the given choices.
Option A is correct. If your scaling events are not based on the right metrics and do not have the right threshold defined, the scaling will not occur as you want it to happen.
Option B is incorrect because if two policies are executed at the same time, Amazon EC2 Auto Scaling follows the policy with the greater impact. For example, if you have one policy to add two instances and another policy to add four instances, Amazon EC2 Auto Scaling adds four instances when both policies are triggered simultaneously. In this question, the EC2 instances are not scaling at all so this option is incorrect.
Option C is incorrect because health checks will help us know the health status of an Auto Scaling instance. It is not a Check if AutoScaling is not working as expected. It is a health check for EC2 instances.
Option D is incorrect because AutoScaling can be used without Load Balancer also.
For more information on Auto Scaling Dynamic Scaling and troubleshooting, please visit the following URLs:
https://aws.amazon.com/premiumsupport/knowledge-center/auto-scaling-troubleshooting/
https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-scale-based-on-demand.html
https://docs.aws.amazon.com/autoscaling/ec2/userguide/ts-as-instancelaunchfailure.html