With AWS Auto Scaling, you can maintain application availability and scale your Amazon EC2 capacity up or down automatically according to the conditions you define. Moreover, Auto Scaling allows you to run your desired number of healthy Amazon EC2 instances across multiple availability zones (AZs).

Additionally, Auto Scaling can also automatically increase the number of Amazon EC2 instances during demand spikes (increase of  CPU utilization or high load) to maintain performance and decrease the instance during less busy periods (Less CPU utilization) to optimize costs.

We can also use AWS Elastic Load Balancer (ELB) for distributing incoming application traffic across designated Amazon Elastic Compute Cloud (Amazon EC2) instances. Whenever there is traffic, based on the load of EC2 servers, it distributes the traffic; the server which has less load will serve the request. This is also known as the least outstanding requests routing algorithm for HTTP and HTTPS listeners, and for TCP listeners ELB uses the Round Robin routing algorithm.