LoadBalancer

A load balancer is a networking component that distributes client requests across multiple servers to optimize resource use, maximize throughput, minimize latency, and ensure high availability. It can be implemented as hardware, software, or a managed cloud service and typically operates at OSI layer 4 (transport) or layer 7 (application). By steering traffic away from any single server, it reduces bottlenecks and provides fault tolerance.

Traffic is directed through the load balancer, which performs health checks on backends and re-routes requests away from failed instances. Common load-balancing strategies include round robin, weighted round robin, least connections, and IP-hash. Many systems support session persistence (sticky sessions) when requests must be consistently handled by the same backend.

Load balancers come in hardware appliances, software solutions, and managed services. Popular software options include Nginx, HAProxy, and Envoy, while hardware products include enterprise appliances from vendors such as F5. Cloud providers offer built-in load balancers, for example AWS Elastic Load Balancing (ALB, NLB, and classic), Google Cloud Load Balancing, and Azure Load Balancer or Application Gateway. DNS-based and anycast approaches are also used in some architectures.

Key considerations include capacity planning, health-check configuration, TLS termination, session persistence requirements, and observability. While load balancing enhances resilience and scalability, improper configuration can create performance overhead or a single point of failure. Proper monitoring, logging, and security controls are essential for effective operation.