title: Allowed memory size exhausted in FlattenException Symfony
body: <p>i got this error at least 20 times each minute on my production server logs.</p>
  
  <p>My website is getting down when visitors number arrives to ~50.</p>
  
  <p>Any suggestion?</p>
  
  <blockquote>
    <p>[Fri Dec 14 23:52:32.339692 2018] [:error] [pid 12588] [client
    81.39.153.171:55104] PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 32 bytes) in
    /vendor/symfony/symfony/src/Symfony/Component/Debug/Exception/FlattenException.php
    on line 269</p>
  </blockquote>