title: Node.js and Android prevent requests at the same time
body: <p>Sorry for the title. I literally have no idea how can I describe my problem here. I have a <strong>download_count</strong> property in my Model. Every time a download from Android App successfully completed, it <strong>GET</strong>s the <strong>download_count</strong> and fires back a <strong>PUT</strong> request with a increased number. </p>
  
  <p>So my problem is, it is highly possible that Device A GETS and before Device A sends back the increased number, Device B gets the same value.</p>
  
  <p>How can I prevent this?</p>