====== Memcached ======

  yum install memcached php-pecl-memcached -y
  systemctl enable memcached

  
заменить 
<code diff core/config/config.inc.php>
-  $config_options = array (); 
+  $config_options = array (
+  'cache_prefix' => 'уникальноезначениедлясайта_',
+  'cache_handler' => 'cache.xPDOMemCached'
+  );
</code>

Очистка
  /usr/bin/echo flush_all > /dev/tcp/localhost/11211