Understand how load balancers distribute traffic for high availability and scalability.
A load balancer is a critical component in most cloud architectures, serving as a 'traffic cop' for your applications. Its primary function is to distribute incoming network traffic across a group of backend servers or resources, often referred to as a server farm or pool. By spreading the load, a load balancer ensures that no single server becomes overwhelmed, which improves application responsiveness and availability. There are several key benefits. First is 'High Availability': if one of the backend servers fails, the load balancer detects the failure and automatically reroutes traffic to the remaining healthy servers, preventing an outage. This is often accomplished through periodic health checks. Second is 'Scalability': as traffic to your application grows, you can add more servers to the backend pool, and the load balancer will immediately begin sending traffic to them. This allows for seamless horizontal scaling without service interruption. Cloud providers typically offer different types of load balancers. Application Load Balancers (ALBs) operate at the application layer (Layer 7) and can make intelligent routing decisions based on the content of the request, such as the URL path or hostname. Network Load Balancers (NLBs) operate at the transport layer (Layer 4) and are capable of handling millions of requests per second with ultra-low latency, ideal for TCP traffic.