Master Nginx Load Balancing: Round Robin, Least Conn, Least Time, IP & Generic Hash

Round Robin

The default Nginx load‑balancing strategy distributes requests sequentially across servers based on each server's weight. With equal weights (default 1), the configuration looks like:

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
}

You can assign custom weights, for example:

upstream backend {
    server backend1.example.com weight=5;
    server backend2.example.com;
}

Least Connections

This method sends each request to the server with the fewest active connections.

upstream backend {
    least_conn;
    server backend1.example.com;
    server backend2.example.com;
}

Least Time

Requests are directed to the server with the smallest response latency. Latency can be measured either from the first byte received ( header) or from the complete response ( last_byte).

upstream backend {
    least_time header;
    server backend1.example.com;
    server backend2.example.com;
}

IP Hash

By hashing the client IP, Nginx consistently routes requests from the same client to the same server, helping maintain session affinity.

upstream backend {
    ip_hash;
    server backend1.example.com;
    server backend2.example.com;
}

Generic Hash

This method hashes a user‑specified key, such as a variable or a combination of values, allowing custom load‑balancing criteria.

upstream backend {
    hash $request_uri consistent;
    server backend1.example.com;
    server backend2.example.com;
}