Sticky sessions in Lighttpd

Web server overhead is never the main cost of a dynamic request - database queries and complex templates use much more resources and every half decent web server can serve hundreds of requests per second, even manage.py runserver in django with an empty template.

Just pick whatever server you know best. I've successfully deployed a site on apache/mod_wsgi, see this answer for details.

Also, "high traffic" is pretty subjective. A number would be more useful.

Make sure you enable lighttpd's mod_proxy first. To have all of the requests for test.com sent to the Node.js backend (assuming it's on localhost; correct?):

$HTTP["host"] == "test.com" {
  proxy.server  = ( "" => (
    ( "host" => "127.0.0.1", "port" => 3000 )
  ) )
}