Auto-scaling is the ability of a system to scale itself automatically based on the triggers like- crashing of a server or low performance.
AWS extensively supports Auto-scaling. It provides tools to create, configure and automatically start new instances without any manual intervention. We can set the thresholds at which new instances will come up. Or we can monitor the metrics like API response time, number of requests per seconds and based on these metrics, let the AWS provision and start new servers.