On Thu, Sep 4, 2014 at 10:38 PM, Daniel Schwen <lists@schwen.de> wrote:

I'm wondering if thumb.php (although it internally reuses existing
thumbnails) play nicely with the varnish cache layer. If you get to a
point where you have to execute a PHP script you are already
generating more load than necessary.

Special:Redirect is a PHP script as well. If you want to avoid circumventing varnish, you need to guess the thumbnail URL on your own. That's very hard if you want to cover all the edge cases.