AWS Elastic Load Balancer: Guide to High Availability and Scalability

In today’s cloud-first world, ensuring high availability, scalability, and fault tolerance is crucial for building robust applications. AWS Elastic Load Balancer (ELB) is a powerful service designed to distribute incoming traffic across multiple targets, such as EC2 instances, containers, IP addresses, and Lambda functions. This post provides an overview of ELB and its key options, empowering you to select the right load balancer for your use case.

AWS Elastic Load Balancer automatically distributes incoming application or network traffic across multiple targets in one or more Availability Zones. By acting as a traffic distribution layer, ELB enhances fault tolerance, scalability, and availability, ensuring your applications can handle varying levels of demand seamlessly.

Types of Elastic Load Balancers

1. Application Load Balancer (ALB)

The Application Load Balancer is ideal for HTTP/HTTPS traffic. Operating at the application layer, ALB allows you to route traffic based on advanced request characteristics. This makes it an excellent choice for microservices-based architectures, web applications, and RESTful APIs.

Use Case Example: Imagine hosting an e-commerce platform. ALB can direct traffic to different microservices based on URL paths—/cart traffic goes to a cart microservice, and /checkout traffic goes to a payment microservice.

1. Network Load Balancer (NLB)
   
   The Network Load Balancer is designed for TCP and UDP traffic and operates at the transport layer. It is built to handle high-throughput, low-latency workloads and can scale to millions of requests per second.
   
   Use Case Example: If you’re running a real-time gaming server or financial application requiring low latency and high throughput, NLB ensures seamless performance even under extreme traffic spikes.
   

2. Gateway Load Balancer (GLB)
   
   The Gateway Load Balancer simplifies the deployment and management of third-party virtual appliances by combining the functionalities of a load balancer and a gateway. It’s ideal for scenarios where traffic must pass through virtual appliances such as firewalls, intrusion detection systems, or network monitoring tools.
   
   Use Case Example: For a highly secure application requiring advanced traffic inspection through a virtual firewall, GLB efficiently routes traffic through the security appliance, ensuring robust protection without manual intervention.