Load balancer (Networking)

Load balancing across multiple application instances is a commonly used technique for optimizing resource utilization, maximizing throughput, reducing latency, and ensuring fault‑tolerant configurations.

Load balancing in Nginx is configured using upstream directive..

• Supported load balancing algorithms: Round Robin, Least Connections, IP Hash, Generic Hash, Least Time (Nginx Plus), Random
• Sticky methods (NGINX Plus): Sticky cookie, Sticky route (NGINX Plus), Sticky learn

Network load balancer can provide service for different protocols, such as TCP, UDP, HTTP or HTTPS.

Typical options:

• Listening port
• FQDN
• Protocol: TCP, UDP, HTTP, HTTPS, Websockets
• Destination servers and destination port
• Load Balancing algorithm: WRR, weighted least connection, source IP hash
• Sticky session

Nginx configuration example

upstream backend {
    # no load balancing method is specified for Round Robin. Other options: least_conn, ip_hash, least_time header, random two least_time=last_byte
    server backend1.example.com slow_start=30s;
    server backend2.example.com max_conns=3;
    server backend3.example.com;
    server 192.0.0.1 backup;
}

Related terms

• Amazon Elastic Load Balancer (ELB)
• Load Balancer as a Service (LBaaS)

See also

• HTTP, HTTP client, HTTP/1.1, HTTP/2, HTTP/3, HTTPS, HSTS CSR, TLS, SSL, openSSL, WebSockets, WebRTC, ssl_certificate QUIC, HPKP, CT, List of HTTP status codes, URL redirection, Content-type:, Webhook, HTTP headers, --insecure, Axios HTTP client, HTTP cookies, HTTP ETag, Hypertext Transfer Protocol -- HTTP/1.1
• Proxy servers: Squid, Reverse proxy, Nginx, HAProxy, Varnish, Load balancer, Load Balancer as a Service (LBaaS), Symantec proxySG and Advanced Secure Gateway (ASG), Traefik, tinyproxy, Proxyrack, Luminati Networks, SOCKS, Envoy Proxy
• Traefik

https://docs.nginx.com/nginx/admin-guide/load-balancer/http-load-balancer/#overview