Question: I have a EKS cluster with min 3 and max 6 nodes, Created auto scaling group for this setup, How can i implement auto scale of nodes when spike up/down on Memory usage since there is no such metric in Auto scaling group like cpu.
Can somebody please suggest me clear steps i am new to this setup .

Answer: 
Out of the box ASG does not support scaling based on the memory utilization.
You`ll have to use custom metric to do that.

[Here](https://medium.com/@lvthillo/aws-auto-scaling-based-on-memory-utilization-in-cloudformation-159676b6f4d6) is way how to do that.

Have you considered using CloudWatch alarms to monitor your nodes?
The scripts can collect memory parameters that can be used later.

See [here](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/mon-scripts.html) how to set it up.
You need to deploy cluster autoscaler which will increase or decreased number of nodes for you. 

See the [official docs](https://github.com/kubernetes/autoscaler/tree/master/cluster-autoscaler).