How to Proxy Multiple Backends in Nginx: Simple Guide

To proxy multiple backends in nginx, define separate location blocks for each backend or use an upstream block to group servers. Then use proxy_pass inside each location to forward requests to the correct backend.

Syntax

Use location blocks to match request paths and proxy_pass to forward requests to backend servers. Optionally, group multiple backends with upstream for load balancing.

• location /path/ { proxy_pass http://backend; }: forwards requests matching /path/ to backend.
• upstream backend { server backend1; server backend2; }: defines a group of backend servers.

nginx

http {
    upstream backend_group {
        server backend1.example.com;
        server backend2.example.com;
    }

    server {
        listen 80;

        location /app1/ {
            proxy_pass http://backend1.example.com/;
        }

        location /app2/ {
            proxy_pass http://backend2.example.com/;
        }

        location /appgroup/ {
            proxy_pass http://backend_group;
        }
    }
}

Example

This example shows how to proxy requests to two different backends based on URL path, and how to use an upstream group for load balancing multiple servers.

nginx

http {
    upstream backend_servers {
        server 192.168.1.10:8080;
        server 192.168.1.11:8080;
    }

    server {
        listen 80;

        location /service1/ {
            proxy_pass http://192.168.1.20:5000/;
        }

        location /service2/ {
            proxy_pass http://192.168.1.21:6000/;
        }

        location /loadbalanced/ {
            proxy_pass http://backend_servers;
        }
    }
}

Output

Nginx listens on port 80 and forwards requests:
- /service1/ to 192.168.1.20:5000
- /service2/ to 192.168.1.21:6000
- /loadbalanced/ to either 192.168.1.10:8080 or 192.168.1.11:8080 (load balanced)

Common Pitfalls

• Forgetting the trailing slash in proxy_pass can cause incorrect URL forwarding.
• Not defining upstream blocks properly leads to load balancing failure.
• Overlapping location blocks can cause unexpected routing.
• Missing proxy_set_header Host $host; can break backend host header expectations.

nginx

server {
    listen 80;

    # Wrong: missing trailing slash causes wrong URL forwarding
    location /app/ {
        proxy_pass http://backend.com;
    }

    # Correct: trailing slash preserves path
    location /app/ {
        proxy_pass http://backend.com/;
    }
}

Quick Reference

Directive	Purpose	Example
location	Matches request URI path	location /api/ { ... }
proxy_pass	Forwards request to backend	proxy_pass http://backend;
upstream	Defines backend server group	upstream backend { server 1.1.1.1; server 2.2.2.2; }
proxy_set_header	Sets headers sent to backend	proxy_set_header Host $host;

Key Takeaways

Use separate location blocks with proxy_pass to route to different backends.

Group multiple backend servers with upstream for load balancing.

Always include trailing slash in proxy_pass URL to preserve request paths.

Set proper headers like Host to ensure backend compatibility.

Avoid overlapping location blocks to prevent routing conflicts.