Example nginx/puma conf file.

nginx.conf

upstream example_name {
  server unix:///var/www/example_name/shared/sockets/puma.sock;
}

server {
  listen 80;
  server_name example_name.com;
  root /var/www/example_name/current/public;

  location / {

    if ($request_method = 'OPTIONS') {
      add_header 'Access-Control-Allow-Origin' $http_origin;
      add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS';
      add_header 'Access-Control-Allow-Headers' 'Content-Type, Accept';
      add_header 'Access-Control-Max-Age' '1728000';
      add_header 'Content-Type' 'text/plain; charset=UTF-8';
      return 200;
    }

    proxy_pass http://example_name;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  }

  location ~ ^/(assets)/  {
    root /var/www/example_name/current/public;
    gzip_static on; # to serve pre-gzipped version
    expires max;
    add_header Cache-Control public;
  }
}