AWS Auto Scaling Group (ASG) Introduction

What is AWS Auto Scaling Group (ASG)?

ASG is a collection of EC2 instances managed as a single unit, these EC2 instances is treated as a logical grouping for the purposes of automatic scaling and management.

In real-life, the load on our application can change, this is where ASG come into play. We can quickly scale up or down application servers.

The goal of an ASG:

• Scale out (add EC2 instances) to handle increased load.

• Scale in (remove EC2 instances) for the decreased load.

• Ensure we have a minimum and maximum number of EC2 instances running.

• Automatically register new instances to a load balancer.

• It can re-create an EC2 instance in case the previous one is terminated.

• ASG is free, we only pay for the underlying EC2 instances.

ASG Attributes

• ASG Launch Template

• It has Min Size/Max size / Initial Capacity

• Scaling Policies (we specify some criteria when ASG should scale up or down, like: Average CPU, or custom metric): It is possible to scale an ASG based on CloudWatch alarms.