Load Balancing and Auto Scaling
Build an Application Load Balancer backed by an Auto Scaling Group using Launch Templates, configure CPU-based scaling policies, and verify that the group replaces an unhealthy instance automatically.
Prerequisites: An AWS account, AWS CLI v2 configured, the VPC and subnets from the EC2 and VPC project (or a VPC with at least two public subnets in different AZs).
An Application Load Balancer (ALB) is a Layer-7 load balancer — it understands HTTP/HTTPS and can route based on path, hostname, headers, and more. Combined with an Auto Scaling Group, you get a system that handles variable load (the ASG adds/removes instances based on demand) and self-heals (the ASG replaces instances the ALB health check marks unhealthy). This combination is the backbone of most stateless web application architectures on AWS.
The correct API sequence matters here: create the target group first, then the ALB and listener pointing at it, then the ASG with the target group ARN. This is the order AWS's own official tutorial follows.
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