Nginx example to redirect users to a "Comming soon portal" if they are not developers.

localhost.conf

server {
  listen 80;

  server_name localhost;

  location @until {
    # Static "comming soon" directory with index.html and assets
    root /var/www/;
    index index.html;
  }

  location /let-me-in {
    # Set a cookie to allow this user see the real site!
    add_header Set-Cookie dev_access=1;
    return 301 http://localhost/;
  }

  location / {
    # If HTTP Error 418 is raised, we "render" @until location
    # 418 is the code for "internal redirection" used by nginx
    error_page 418 = @until;
    recursive_error_pages on;

    # Tricky part. Check cookie and deny access if not set
    set $developer N;
    if ($http_cookie ~* "dev_access") {
      set $developer S;
    }

    # No cookie, so no access. Redirect to "@until"
    if ($developer = N) {
      return 418;
    }

    # Normal site, let the user see it
    root /path/to/rails/app/public;

    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;
    proxy_pass http://127.0.0.1:3000/;
  }
}