title: Scaling a chat app - short polling vs. long polling (AJAX, PHP)
body: <p>I run a website where users can chat with each other through the browser (think Facebook chat). What is the best way to handle the live interaction? (Right now I have a poll going every 30 seconds to update online users and new incoming messages, and another poll going on chat pages every second to get new messages.)</p>
  
  <p>Things I've considered:</p>
  
  <ul>
  <li>HTML5 Web Sockets: didn't use this because it doesn't work in all browsers (only chrome).</li>
  <li>Flash Sockets: didn't use this because I wanted to eventually support mobile web.</li>
  </ul>
  
  <p>Right now, I am using short polling because I don't know how scalable AJAX long polling would be. I'm running a VPS server from servint right now (running apache). Should I use long polling or short polling? I don't need absolutely immediate response times (just "good enough" for a chat app). Is short polling this often with a few hundred-thousand users going to kill my server? How do I scale this, please help!</p>