Load Balancing

A load balancer sits in front of several identical servers and spreads incoming requests across them. It’s how you scale horizontally — add more machines instead of buying a bigger one.

flowchart LR
  C[Client] --> LB[Load Balancer]
  LB --> S1[Server 1]
  LB --> S2[Server 2]
  LB --> S3[Server 3]

Common strategies

• Round-robin — hand each new request to the next server in turn.
• Least-connections — send to whichever server is currently least busy.

Load Balancing

When one server can’t handle all your traffic, you add more servers. But now — which one should each visitor talk to? A load balancer is the traffic cop that stands in front and spreads requests evenly across your servers.

The setup

flowchart LR
  C[Visitors] --> LB[Load Balancer]
  LB --> S1[Server 1]
  LB --> S2[Server 2]
  LB --> S3[Server 3]

Every request hits the load balancer first, and it decides which server handles it. This lets you scale out — handle more users by adding cheap servers, instead of buying one giant expensive machine.

How it decides

Two common approaches:

• Round-robin — take turns: server 1, then 2, then 3, then back to 1. Simple and fair.
• Least-connections — send each request to whichever server is currently least busy. Smarter when some requests take longer than others.

Bonus: it handles dead servers

The load balancer regularly pings each server with a health check (“you alive?”). If a server stops responding, the balancer quietly stops sending traffic to it — so one crashed machine doesn’t break your site. Users never notice.

In one sentence

A load balancer sits in front of multiple servers and spreads incoming requests across them (round-robin or least-busy), letting you scale by adding servers — and it routes around any server that fails its health check.

Want to go deeper?

Switch to Expert mode above for more on strategies and health-check behavior.