Load Balancer

A device or software that distributes network traffic across multiple servers to ensure high availability, reliability, and optimal resource utilization.

What is a Load Balancer?

A load balancer distributes incoming network traffic across multiple backend servers. This distribution ensures no single server bears too much demand, improving application availability, responsiveness, and fault tolerance.

How Load Balancing Works

Load balancers sit between clients and servers, receiving requests and directing them based on configured algorithms. They monitor server health, removing unhealthy servers from the pool and returning them when recovered.

Load Balancing Algorithms

Round Robin: Requests distributed sequentially
Least Connections: Directs to server with fewest active connections
IP Hash: Same client IP always goes to same server
Weighted: Servers receive traffic proportional to assigned weights
Least Response Time: Chooses fastest responding server

Types of Load Balancers

Layer 4 (Transport): Routes based on IP and TCP/UDP ports
Layer 7 (Application): Routes based on content (URLs, headers, cookies)
Hardware: Dedicated appliances
Software: Applications like HAProxy, Nginx
Cloud: AWS ALB, Azure Load Balancer, GCP Load Balancing

Benefits

High availability through redundancy
Scalability by adding servers
Flexibility for maintenance windows
SSL termination offloading
Global server load balancing (GSLB)