Load Balancer

Definitions

1. A load balancer is a device or piece of software that distributes incoming network traffic across multiple servers to ensure no single server becomes overwhelmed. By spreading requests evenly, load balancers improve application availability, reliability, and response times. They operate at different layers of the network stack. Layer 4 (transport) balancers route traffic based on IP address and TCP port, while Layer 7 (application) balancers can inspect HTTP headers, cookies, or URL paths to make smarter routing decisions. Common algorithms include round-robin, least connections, and IP hash. Load balancers also perform health checks, automatically removing unhealthy servers from the pool and reintroducing them once they recover. Popular implementations include Nginx, HAProxy, AWS Elastic Load Balancing, and cloud-native options from every major provider. In modern architectures, load balancers are essential for horizontal scaling, zero-downtime deployments, and distributing traffic across multiple availability zones.

   In plain English: A traffic cop for servers — directing incoming users to different copies of a website so no single server gets overwhelmed.

Related Terms

• Nginx
• CDN
• Circuit Breaker
• reverse proxy
• Failover
• Active-Active
• Warm Standby
• Mirror
• Network Interface
• Performance Monitoring
• Port
• Proxy
• Registry
• Router
• Consul
• Blue-Green
• Cloud Networking