? What is EC2 Auto Scaling?

EC2 Auto Scaling is a feature that automatically adjusts the number of Amazon EC2 instances in your application based on demand.

It helps ensure:

• Your app always has the right amount of compute capacity.

• You only pay for what you use.

? Why Use EC2 Auto Scaling?

? How EC2 Auto Scaling Works

1. Auto Scaling Group (ASG):

   • A collection of EC2 instances managed as a group.

   • You define:

     • Min number of instances

     • Max number of instances

     • Desired capacity (default target)

2. Launch Template / Configuration:

   • Tells Auto Scaling what kind of EC2 instances to launch (type, AMI, key pair, etc.).

3. Scaling Policies:

   • Rules that define when to add/remove instances.

   • Types:

     • Dynamic Scaling – based on CloudWatch alarms (e.g., CPU > 80%)

     • Scheduled Scaling – based on a time (e.g., scale up at 9 AM daily)

     • Predictive Scaling – uses machine learning to forecast demand.

4. Health Checks:

   • Auto Scaling automatically replaces unhealthy EC2 instances.

? Example Use Case

Imagine you run an e-commerce website:

• During the day: Traffic is high ? Auto Scaling adds EC2 instances

• At night: Low traffic ? Auto Scaling terminates extra instances

This ensures:? High performance during busy hours
? Low cost during idle times

? Integration with Other Services

? Sample Scaling Policy

json
If average CPU utilization > 75% for 5 minutes? Add 1 EC2 instanceIf average CPU utilization < 30% for 10 minutes? Remove 1 EC2 instance

? Key Terms to Remember

• ASG (Auto Scaling Group) – the group of instances managed by auto scaling.

• Launch Template – defines what kind of instance to launch.

• Scaling Policy – when and how to scale.

• CloudWatch Alarm – used to trigger scaling actions.

? Summary