Rate Limiter

A rate limiter controls the number of requests a client can make to a service within a given time window. In system design interviews, rate limiting appears whenever you discuss API design, security, or protecting backend services from being overwhelmed.

This page covers what you need to know for interviews: why rate limiting matters, the algorithms that power it, how to design a distributed rate limiter, and the trade-offs between different approaches. Understanding these concepts helps you design systems that stay available under load and protect against abuse.