This approach relies on the backend proxying `/api` to the API. In other words, the client requests http://www.example.com/api/foo http://www.example.com/api/fo

This approach relies on the backend proxying `/api` to the API. In other words, the client requests http://www.example.com/api/foo http://www.example.com/api/foo, then the backend goes off and fetches http://api.example.com/foo http://api.example.com/foo, then sends it back to the client. You can’t do that because in your case only the client can connect to the local networks; your backend has no access.