Load balancer

A load balancer distributes incoming requests or connections across multiple service instances.

Format
Performance & CDN
Updated
Updated
Glossary Performance & CDN
Load balancer Aliases: traffic distributor, reverse proxy load balancer.

Definition

A load balancer distributes incoming requests or connections across multiple service instances.

How it works

Using health checks and routing rules, a load balancer steers each request to an instance that can handle it and skips any that are down. It is a key ingredient for scaling and availability — but only if the application cooperates. Sessions, uploads, and the database all need a story for running across more than one machine.

Example: A load balancer sends web requests to whichever of three application servers is healthy and least busy.

Often confused: The load balancer spreads the traffic; it cannot make a single-instance application safe to duplicate.

Sources

Last reviewed 2026-07-19.