I own a small messaging platform and I'm trying to make it live, so everything needs to work without any refresh. Messages are sent with Ajax and the procedure is refresh-free. I'm also trying to make sure that when Alice sends a message to Bob, Bob receives it (almost) immediately. For this reason, I'm refreshing the div containing all of the messages every second with this script:

      <script>
         $(document).ready(function() {
         var pageRefresh = 1000;
             setInterval(function() {
                 refresh();
             }, pageRefresh);
         });
         
         function refresh() {
             $("#messagesframe").load(" #messagesframe > *");
         }
      </script>

      <div id="messagesframe">
      <!-- messages displayed here! -->
      </div>

This makes sure that every second the new messages are shown. I have a doubt, however, that this may slow down the application. I am asking you, thus, whether this doubt is well-founded or if this procedure is harmless. Any help is appreciated.

Note: I'm using PHP.