Autoscaling is an approach to automatically scaling out instances based on the resource usage to meet the SLAs by replicating the services to be scaled.
The system automatically detects an increase in traffic, spins up additional instances, and makes them available for traffic handling. Similarly, when the traffic volumes go down, the system automatically detects and reduces the number of instances by taking active instances back from the service:
As shown in the preceding diagram, autoscaling is done, generally, using a set of reserve machines.
As many of the cloud subscriptions are based on a pay-as-you-go ...