Overview
An Auto Scaling Group (ASG) contains a collection of EC2 instances that are treated as a logical grouping for the purposes of automatic scaling and management. An ASG also enables you to use Amazon EC2 Auto Scaling features such as health check replacements and scaling policies.
Key Concepts
- Desired Capacity: The number of instances the group should maintain.
- Minimum/Maximum Size: The boundaries for scaling operations.
- Scaling Policies: Rules that define when to add or remove instances (e.g., based on CPU utilization).
- Launch Template: Defines the configuration of the instances (AMI, instance type, security groups).
Benefits
- Fault Tolerance: Automatically replaces failed instances.
- Cost Efficiency: Scales down during low demand to save money.
- Availability: Ensures the application has enough capacity to handle current traffic.