In the dynamic world of cloud computing, Elastic Load Balancers (ELBs) play a crucial role in ensuring high availability, scalability, and efficient distribution of incoming traffic across backend servers. In this blog post, we’ll delve into the fundamentals of AWS ELBs, explore their types, and provide practical examples.

What is Elastic Load Balancing?

Elastic Load Balancing is a service provided by Amazon Web Services (AWS) that automatically distributes incoming traffic across a group of backend servers. Here’s why it matters:

• Scalability: ELBs allow your application to handle increased traffic by distributing it efficiently.
• Fault Tolerance: If any backend server fails, ELBs automatically route traffic away from the unhealthy target.
• Security: ELBs enhance security by acting as a single entry point for incoming requests.

Types of AWS Load Balancers

1. Classic Load Balancer (CLB)

• The traditional form of load balancer.
• Distributes traffic among instances.
• Operates at both the connection level (TCP/SSL) and request level (HTTP/HTTPS).
• Lacks intelligence for host-based or path-based routing.

2. Application Load Balancer (ALB)

• Works at the Application layer (Layer 7) of the OSI model.
• Ideal for routing decisions related to HTTP and HTTPS traffic.
• Supports path-based and host-based routing.
• Example: Routing requests to different microservices based on URL paths.

3. Network Load Balancer (NLB)

• Operates at the Transport layer (Layer 4) of the OSI model.
• Handles millions of requests per second.
• Mainly used for load-balancing TCP traffic.
• Example: Distributing traffic to backend servers hosting gaming sessions.

4. Gateway Load Balancer (GLB)

• Combines a transparent network gateway with load balancing.
• Used for deploying, scaling, and managing virtual appliances like firewalls.
• Routes traffic efficiently.
• Example: Deploying a firewall appliance in front of your VPC.

Practical Examples

Example 1: ALB for Microservices

Suppose you have a web application with multiple microservices (user service, product service, payment service). An ALB can route requests based on URL paths:

• /users → User Service
• /products → Product Service
• /payments → Payment Service

Example 2: NLB for Gaming Servers

Imagine an online multiplayer game with thousands of players. NLB can distribute incoming game traffic to backend servers hosting gaming sessions. It ensures low latency and high throughput.

Conclusion

AWS Elastic Load Balancers are essential components for building scalable, fault-tolerant, and secure applications. By understanding their types and functions, you can optimize your infrastructure and deliver a seamless experience to your users.