EC2 Auto Scaling Groups CheatSheet

An ASG isa collection of EC2 instances grouped for scaling and management
Scaling Out is when add servers
Scaling In is when you remove servers
Scaling Up is when you increase the size of an instance (eg. updating Launch Configuration with larger size)
Size of an ASG is based on a Min, Max and Desired Capacity
Target Scaling policy scales based on when a target value for a metric is breached eg. Average CPU Utilization exceed 75%
*Simple Scaling policy triggers a scaling when an alarm is breached
Scaling Policy with Steps is the new version of Simple Scaling policy and allows you to create steps based on escalation alarm values.
Desired Capacity is how many EC2 instances you want to ideally run
An ASG will always launch instances to meet minimum capacity
Health checks determine the current state of an instance in the ASG
Health checks can be run against either an ELB or the EC2 instances
When an Autoscaling launches a new instance it uses a Launch Configuration which holds the conf
values for that new instance eg. AMI, InstanceType, Role
Launch Configurations cannot be edited and must be cloned or a new one created
Launch Configurations must be manually updated in by editing the Auto Scaling settings.