Rails + Angular/Ember/React on the same server

app.conf

#
# Define your upstream cluster
#
upstream rails {
  server 0.0.0.0:3000 fail_timeout=0;
}

server {
    listen   80;
    server_name your_app.dev;

    #
    # This is the proxy to your API
    #
    location ~ ^/v1/api/(.+)$ {
        sendfile off;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_set_header X-Real-IP         $remote_addr;
        proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Protocol   $scheme;
        proxy_pass http://rails;
    }

    #
    # This section serves the index.html of your Ember app
    #
    location ~ ^/$ {
        sendfile off; # Don't know why, but necessary
        alias /path/to/ember/;
        try_files index.html =500; #index.html can not be found
    }

    #
    # This section serves the other files of your Ember app
    #
    location ~ ^/(.+)$ {
        sendfile off; # Same as above
        alias /path/to/ember/;
        try_files /$1 =404;
    }
}