Load Balancing Algorithms

When your website becomes popular and a single server can't handle all the traffic, you need multiple servers to share the load. But how do you decide which request goes to which server? This is where load balancing algorithms come in.

Let's look at the most common load balancing algorithms and understand when to use each one.

Round Robin is the simplest approach. The requests are distributed to servers in a circular order. Server 1 gets the first request, Server 2 gets the second, and so on. When we reach the last server, we start over from Server 1. While simple to implement, Round Robin assumes all servers are equally capable and all requests take similar time to process.

Weighted Round Robin improves on this by assigning weights to servers based on their capacity. A server with weight 2 will receive twice as many requests as a server with weight 1. This works well when you have servers with different processing powers.

Least Connections sends new requests to the server handling the fewest active connections. This is particularly useful when request processing times vary significantly. For example, in an e-commerce site where some users browse quickly while others spend time checking out, Least Connections ensures no server gets overwhelmed.

Least Response Time goes a step further by considering both the number of active connections and the server's response time. This helps identify servers that might be struggling even if they have fewer connections.

IP Hash uses the client's IP address to determine which server should handle the request. This ensures that requests from the same client always go to the same server, which is useful when you need to maintain session data.