Standby mode
Auto Scaling provides you with an option for transition from an InService EC2 instance to Standby mode, so that you can perform the required maintenance, update the EC2, and join the instance back to the Auto Scaling Group. When an instance is transitioned to the Standby mode, it does not receive any traffic from the load balancer, but it is still part of the Auto Scaling Group.
As soon as an EC2 instance is transitioned to the Standby state, Auto Scaling will decrement the desired capacity. This is to avoid launching the new instance while you have this instance on standby. If you tell Auto Scaling not to decrement the desired capacity, then a new EC2 instance will be launched as a replacement. Once the instance is in standby mode, Auto Scaling does not perform any health checks on the instance. You can use the Enter-ASStandby cmdlet to transition the EC2 instance into standby mode.
PS C:\> Enter-ASStandby -InstanceId i-05ba9441e9d65e0ff -AutoScalingGroupName WebAppASG -ShouldDecrementDesiredCapacity...
