Automatically adjusting the number of servers based on demand. Like a restaurant that opens more tables during busy hours and closes them when it's quiet.
During Black Friday, Auto Scaling automatically adds more EC2 instances to handle increased website traffic, then removes them when traffic returns to normal.
All four scale compute instances up/down based on metrics or schedules. AWS focuses on Auto Scaling Groups for EC2; Azure uses VM Scale Sets with Autoscale rules; GCP uses Managed Instance Groups with an autoscaler; OCI uses Instance Pools with autoscaling policies. Each integrates with its load balancer and monitoring service for metric-driven scaling.