upstream backend {
    # Load balancing method (optional, defaults to round-robin)
    least_conn;  # or ip_hash, or omit for round-robin
    
    # Backend servers
    server backend1.example.com:8080 weight=3;
    server backend2.example.com:8080 weight=2;
    server backend3.example.com:8080;
    
    # Backup server (used when all primary servers are down)
    server backup.example.com:8080 backup;
    
    # Health check parameters
    keepalive 32;
}

server {
    listen 80;
    server_name example.com;
    
    location / {
        proxy_pass http://backend;
        
        # Essential proxy headers
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        
        # Timeouts
        proxy_connect_timeout 60s;
        proxy_send_timeout 60s;
        proxy_read_timeout 60s;
        
        # Buffering
        proxy_buffering on;
        proxy_buffer_size 4k;
        proxy_buffers 8 4k;
    }
}

upstream backend {
    server backend1.example.com:8080 max_fails=3 fail_timeout=30s;
    server backend2.example.com:8080 max_fails=3 fail_timeout=30s;
    server backend3.example.com:8080 max_fails=3 fail_timeout=30s;
}

# Test configuration
nginx -t

# Reload nginx
nginx -s reload

upstream backend {
    server backend1.example.com:8080;
    server backend2.example.com:8080;
}

upstream backend {
    least_conn;
    server backend1.example.com:8080;
    server backend2.example.com:8080;
}

upstream backend {
    ip_hash;
    server backend1.example.com:8080;
    server backend2.example.com:8080;
}

upstream backend {
    server backend1.example.com:8080 weight=3;  # Gets 3x traffic
    server backend2.example.com:8080 weight=1;
}

location /ws {
    proxy_pass http://backend;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

upstream backend {
    server backend1.example.com:8080;
    server backend2.example.com:8080;
    
    # Requires nginx Plus or third-party module
    sticky cookie srv_id expires=1h domain=.example.com path=/;
}

upstream backend {
    server backend1.example.com:8080 slow_start=30s;
    server backend2.example.com:8080 slow_start=30s;
}