Load Balancing Basics

A Load Balancer is like a “traffic cop” for your application. It sits in front of your many servers and sends each incoming request to the server that can best handle it.

The Problem:

If you have 10,000 users and only one server, that server will get overwhelmed. If you have 3 servers, how do you decide which user goes to which server?

The Solution: The Load Balancer

The load balancer receives every request first and then passes it along to one of the servers.

Simple Diagram

       [ User 1 ] [ User 2 ] [ User 3 ]
                 \   |   /
                  v  v  v
             [ Load Balancer ]
             /       |       \
     [ Server 1 ] [ Server 2 ] [ Server 3 ]

How It Decides (Algorithms)

How does the “traffic cop” decide which server to use?

• Round Robin: Go in order (Server 1, then Server 2, then Server 3, then back to 1).
• Least Connections: Send the request to the server with the fewest active users right now.
• IP Hash: Always send a specific user to the same server.

Why Use It?

1. Redundancy: If Server 1 crashes, the Load Balancer just stops sending traffic there. Users don’t even notice.
2. Scalability: You can add 10 more servers behind the Load Balancer without changing anything for the user.
3. Speed: It prevents any single server from getting too busy.

Next: Caching Basics