Javascript - 如何减少抓取延迟并使其更快？

I have this little

Packets sender code:

public function spinboxAction() {
    $this->_response->setHeader('Access-Control-Allow-Origin', '*');       
    $this->_helper->layout()->disableLayout();
    $this->_helper->viewRenderer->setNoRender();   
    $post = $this->getRequest()->getQuery();
    $this->db = Application_Model_Db::db_load();               
    $sql = "select 
            u.id, u.username, u.status, callstatus, callername,             
            namedisplay,
            theme,debug, p.username as pusername, (select kiosk 
                                                   from sh_av_spform
                                                   where `status` IS NULL 
                                                   and kiosk=u.username limit 1) as ftodo
            from 
            sh_av_users u 
            inner join sh_av_profile p on u.profileid=p.id            
            where u.groups='c1'";    
    $result = $this->db->fetchAll($sql);    
    $json = '';
    if (count($result) > 0) {
      //$config = new Zend_Config_Ini(APPLICATION_PATH . '/configs/conf.ini', 'production');      
      $todo = false;
      $sql = "select *from sh_av_spform where `status` IS NULL limit 1";
      $todo = $this->db->fetchAll($sql);
      if(count($todo)> 0 ){
        $todo = true;
      } else {
        $todo = false;
      }

      $json = array(
          'result' =>'ok',
          'db' => $result,
          'todo' => $todo
      );      
    }   else {
      $json = array(
          'result' => 'fail',
          'db' =>$result,
          'todo' => false
      );        
    } 

    $this->getResponse()
            ->setHeader('Content-Type', 'application/json')
            ->setBody(Zend_Json::encode($json))
            ->sendResponse();

    exit;
  } 

Packets receiver code:

function crawl() {
  maincrawl_timer = setTimeout(function() {
    var s1 = $.get(submit_url + '/spinbox', {
        action: 'spinbox',
        ousername: main_username,
        status: 'offline'
    }, function(msg) {
      for(bee in msg.db) {
        //...        
      }
    }, 'json'); 

    s1.always(function() {
      console.log('>>> crawl started, autocall state: ', global_autocall);
      crawl();
    });

  }, 2000 );
}

crawl();

On Packets receiver end is Google Chrome stable (Windows 8.1 Pro). Its taking a while to get the packets like you can see below 204ms sometimes its 500ms but the application is suffering a lot of issue for this. Sometimes the packet is completely lost not being sent to server as a result the application fails on production site.

How to speed this process little more faster so that it can be done within less then 204ms please?