What Is Load Balancing

 What Is Load Balancing?

Load balancing is the process of distributing network traffic across multiple servers. This ensures no single server bears too much demand. By spreading the work evenly, load balancing improves application responsiveness. It also increases availability of applications and websites for users. Modern applications cannot run without load balancers.

A load balancer acts as the “traffic cop” sitting in front of your servers and routing client requests across all servers capable of fulfilling those requests in a manner that maximizes speed and capacity utilization and ensures that no one server is overworked, which could degrade performance. If a single server goes down, the load balancer redirects traffic to the remaining online servers. When a new server is added to the server group, the load balancer automatically starts to send requests to it.

In this manner, a load balancer performs the following functions:

1. Distributes client requests or network load efficiently across multiple servers
2. Ensures high availability and reliability by sending requests only to servers that are online
3. Provides the flexibility to add or subtract servers as demand dictates

Question: There is a website run by 2 servers. These 2 servers balances the load using Load Balancer. So, if 1 session is created on 1 server and say load is shift to another server immediately, then how session is maintained?

This is where the concept of "Sticky Sessions" or "Session Affinity" comes into play.

Sticky Sessions: By default, a Classic Load Balancer routes each request independently to the registered instance with the smallest load. However, you can use the sticky session feature (also known as session affinity), which enables the load balancer to bind a user's session to a specific instance. This ensures that all requests from the user during the session are sent to the same instance. Read more

In .Net there are two concepts called StateServer or SQLServer which are the recommendations to get the session information out of the execution process in the servers, so that's the idea, isolate the sessions in a different server or process, you can read a little bit here: