Load Balancer

A load balancer distributes incoming requests across multiple servers to prevent any single server from becoming overwhelmed. In system design interviews, load balancers appear in virtually every architecture diagram you draw—they're fundamental to achieving scalability, availability, and performance.

This page covers what you need to know for interviews: how load balancers work, the algorithms they use, the difference between L4 and L7 balancing, and when to discuss global versus local load balancing. Understanding these concepts helps you design systems that handle millions of requests without falling over.