title: Keeping millions of thumbnails updated
body: <p>We have a massive collection of images (think 30+ million images).</p>
  
  <p>The image files are quite big, so it's slow to work with the files in our application for sorting images etc.</p>
  
  <p>We have therefore decided to make thumbnails of all the files (we have the necessary storage + processing power for generating the thumbnails).</p>
  
  <p>Now the problem is that sometimes an image needs to be deleted or replaced with an updated image - and we do of course want the thumbnails to stay updated, so they are also deleted/replaced if images are deleted/replaced.</p>
  
  <p>Do we really need to implement our own service/program/script for this - or can someone recommend an existing service/program/script that does this?</p>
  
  <p>Thanks!</p>