What is Auto Scalling Group in AWS? (34 of 285 technotes in 2015)

Auto scaling in AWS is a way to increase/decrease  the infrastructure required to run a server in AWS purely based on the demand.

• Its helps to scale up/down the EC2 capacity based on the conditions defined.
  
• Automatically increases the number of EC2 instances to handle demand.
• Decreases/stops  the number of EC2 instances when demand reduces to reduce cost.
• Note: all server / nodes should be in auto start mode for Auto scaling to work properly.

For example:

In a typical Websphere Clustered environment with multiple nodes and a Load balancer, we can create a Auto Scaling Group to start /stop nodes based on demand.

References: http://aws.amazon.com/autoscaling/details/