AWS Load Balancing: Optimize Load Distribution between Your Instances.
In the cloud, your applications must be available and fast. AWS Load Balancers help you share traffic across multiple servers, so your system stays reliable, scalable, and resilient.
In this article, you'll learn:
What AWS Load Balancers do and why they matter.
How they improve your infrastructure.
How to build a high-availability setup with Terraform.
Key Benefits
1. Always-On Availability
Automatic failover if a server goes down.
Health checks send users only to healthy servers.
Multi-AZ (Availability Zone) setup by default.
2. Smart Traffic Distribution
Load distribution methods: round-robin, least connections, IP hash.
Path-based routing (ALB feature).
Cross-zone load balancing.
3. Built for Scale
Handles sudden traffic spikes automatically.
No manual capacity planning.
Works seamlessly with Auto Scaling.
Why You Should Use It
Reliability: Up to 99.99% SLA with proper configuration.
Cost optimization: Better use of your existing servers.
Security: Centralized SSL certificates + DDoS protection.
Tutorial: Build Your High-Availability App
Goal:
Create 2 EC2 t2.nano instances.
Use Ansible to:
Install Docker.
Launch Nginx to simulate a web server.
Customize each server's homepage.
Create an Application Load Balancer to share traffic.
What You Need
AWS account.
AWS CLI installed.
Terraform installed.
Ansible installed.
Best Practice Setup
For security and easier management, create an IAM user (e.g., user_terraform) with these permissions:
AmazonEC2FullAccessAmazonVPCFullAccessElasticLoadBalancingFullAccessIAMReadOnlyAccess
Project Structure
.
├── ansible
│ ├── common.yaml
│ ├── instance_1.yaml
│ ├── instance_2.yaml
│ └── inventory.tpl
├── environments
│ └── stages
│ ├── main.tf
│ └── outputs.tf
├── keys
│ ├── key
│ └── key.pub
├── LICENSE
├── main.tf
├── modules
│ ├── compute
│ │ ├── main.tf
│ │ ├── outputs.tf
│ │ └── variables.tf
│ ├── loadbalancer
│ │ ├── main.tf
│ │ ├── outputs.tf
│ │ └── variables.tf
│ ├── networking
│ │ ├── main.tf
│ │ ├── outputs.tf
│ │ └── variables.tf
│ └── security
│ ├── main.tf
│ ├── outputs.tf
│ └── variables.tf
├── outputs.tf
├── providers.tf
└── README.md
Steps
Step 1 – Configure AWS CLI
aws configure
Step 2 – Clone the Repository
git clone https://github.com/Ankoay-Feno/app_high_availability.git
cd app_high_availability
Step 3 – Create SSH Key Pair
mkdir keys
ssh-keygen -t rsa -b 4096 -C "user_email@example.com" -f keys/key
Step 4 – Deploy with Terraform
terraform init
terraform plan # Optional
terraform apply --auto-approve
Test Your Setup
for i in {1..20}; do
curl $(terraform output -raw loadbalancer_url)
echo ""
done
You should see alternating responses from your two instances.
