Auto Scaling is a feature of Amazon Web Services (AWS) that allows users to automatically adjust the capacity of their resources in response to changes in demand. AWS Auto Scaling enables users to build scaling plans that automate how groups of different resources respond to changes in demand, optimizing availability, costs, or a balance of both. Auto Scaling monitors applications and automatically adjusts capacity to maintain steady, predictable performance at the lowest possible cost.

Auto Scaling can be used for a variety of AWS resources, including Amazon EC2 instances, Spot Fleets, Amazon ECS tasks, Amazon DynamoDB tables, and Amazon Aurora Replicas. Users can configure a single unified scaling policy per application source, and explore the application to create a scaling plan. Auto Scaling can be configured to scale based on the occurrence of specified conditions (dynamic scaling) or on a schedule.

Benefits of Auto Scaling include better fault tolerance, high availability of resources, better cost management, high reliability of resources, and high flexibility of resources. Auto Scaling allows users to optimize their utilization and cost efficiencies when consuming AWS services so they only pay for the resources they actually need.

Auto Scaling is free to use, and users only pay for the AWS resources needed to run their applications and Amazon CloudWatch monitoring fees. AWS Auto Scaling provides a simple, powerful user interface that lets users build scaling plans for their resources in minutes.