title: How to ProxyPass if the request doesn't correspond to a file
body: <p>I'm trying to implement the following behavior:
  If the request corresponds to a file in <code>/var/www/html</code>, then serve it, else, ProxyPass to a different hostname and port.
  I am aware of the <code>RewriteCond</code> directive and that we can exclude some path from a <code>ProxyPass</code> but that doesn't help me achieve what I want.</p>
  
  <p>At the moment my config looks like this:</p>
  
  <pre><code>&lt;Directory "/var/www/html"&gt;
      Options Indexes FollowSymLinks
      AllowOverride None
      Require all granted
  &lt;/Directory&gt;
  
  &lt;VirtualHost *:80&gt; 
      ProxyPreserveHost On
      ProxyRequests Off
      ProxyPass /backend/ http://server:8080/backend/
      ProxyPassReverse /backend/ http://server:8080/backend/
      ProxyPass / http://client:4000/
      ProxyPassReverse / http://client:4000/
  &lt;/VirtualHost&gt;
  </code></pre>