You have decided that you need to change the instance type of your production instances which are running as part of an AutoScaling group. The entire architecture is deployed using CloudFormation Template. You currently have 4 instances in Production. You cannot have any interruption in service and need to ensure 2 instances are always running during the update. Which of the options below listed can be used for this?

Answer options:

A.AutoScalingRollingUpdate
B.AutoScalingScheduledAction
C.AutoScalingReplacingUpdate
D.AutoScalingIntegrationUpdate

Answer – A
The AWS::AutoScaling::AutoScalingGroup resource supports an UpdatePolicy attribute. This is used to define how an Auto Scaling group resource is updated when an update to the CloudFormation stack occurs. A common approach to updating an Auto Scaling group is to perform a rolling update, which is done by specifying the AutoScalingRollingUpdate policy. According to the parameters specified, this retains the same Auto Scaling group and replaces old instances with new ones.
For more information on Autoscaling updates, please refer to the below link:
https://aws.amazon.com/premiumsupport/knowledge-center/auto-scaling-group-rolling-updates/