Load Balancer

A load balancer is a device or software that distributes network or application traffic across multiple servers. This distribution is designed to optimize resource use, maximize throughput, minimize response time, and avoid overload on any single server. Load balancers are essential in high-traffic network environments, particularly for ensuring reliability and performance of websites, applications, and databases.

A load balancer efficiently routes incoming network traffic across multiple servers (also known as a server farm or server pool) in a way that none of the servers are overburdened. This ensures that application or website performance is optimized.

Load balancers use various algorithms to distribute traffic, such as round-robin, least connections, IP hash, and others. The choice depends on the specific requirements of the environment. Load balancers continuously check the health of servers to ensure traffic is only directed to servers that are currently operational. This helps in avoiding downtime.

Certain applications require that a user's session be maintained on a single server. Load balancers can handle such "sticky sessions" to ensure user experience consistency. Load balancers allow systems to easily scale in response to varying traffic loads. They also enable maintenance and updates without service interruption.

Modern load balancers, often termed as Application Delivery Controllers, offer advanced features like SSL termination, [[application layer]] (Layer 7) load balancing, and other security features. By spreading the workload, load balancers improve application responsiveness and increase availability of applications and websites.

In [[cloud computing]], load balancers are used to distribute traffic across a cloud service's multiple instances. Load balancers can also provide additional security features like protecting against [[Denial of Service (DoS) Attacks]] and managing traffic spikes.