How to Handle Load Balancing in AWS and Use Multiple Instances for a Single Website

What is Load Balancing?

Load balancing is the process of distributing incoming traffic across multiple servers (instances) so that no single server is overwhelmed.

Imagine your website as a restaurant:

• If only one waiter is serving, customers wait longer.
• If there are multiple waiters, the manager assigns customers evenly, and service improves.

That’s exactly what a Load Balancer does for your website.

AWS Elastic Load Balancer (ELB)

AWS provides a managed service called Elastic Load Balancer (ELB). It automatically distributes incoming traffic across multiple EC2 instances.

Types of AWS Load Balancers:

1. Application Load Balancer (ALB) – Best for web applications (works at the application layer, HTTP/HTTPS).
2. Network Load Balancer (NLB) – Best for extreme performance, TCP/UDP traffic.
3. Classic Load Balancer – Older version, not recommended for new projects.

For most websites, ALB is the go-to option.

Using Multiple Instances for One Website

Step 1: Launch Multiple EC2 Instances

• Create EC2 instances with the same application code and configurations.
• You can use AMI (Amazon Machine Image) to replicate the same environment quickly.

Step 2: Put All Instances Behind a Load Balancer

• Create an Application Load Balancer from the AWS console.
• Add your EC2 instances to the Target Group.
• The load balancer will now distribute requests evenly.

Step 3: Configure Auto Scaling (Optional but Recommended)

• Use Auto Scaling Groups to automatically add/remove EC2 instances based on traffic load.
• Example: Add more instances when traffic spikes, remove them when traffic drops.

Step 4: Attach a Domain

• Point your website’s domain (via Route 53 or any DNS) to the Load Balancer’s DNS name.
• This ensures visitors are routed through the load balancer.

Benefits of Load Balancing in AWS

• High availability – if one instance fails, traffic is sent to healthy ones.
• Scalability – easily handle traffic spikes.
• Better performance – faster response times for users.
• Cost optimization – only pay for resources you need.

Example Use Case

• A website running on one EC2 instance starts crashing during peak hours.
• You launch three instances and put them behind an Application Load Balancer.
• Users now experience smooth browsing, and you can sleep peacefully.

Final Thoughts

Load balancing with AWS is a must-have if you expect your website to grow. By combining Elastic Load Balancer with multiple EC2 instances (and optionally Auto Scaling), you can build a robust, scalable, and highly available application without managing complex infrastructure.