I have been trying to speed up a Drupal site and measuring speed through page speed insight. What really has puzzled me for last few weeks of experiments is that node pages score an average of 170-200ms on 'initial server response time' while taxonomy pages (which are far more important from SEO speed point of time) take an average of 720-750ms in terms of initial page response time.
(Drupal 7, Nginx, Php-fpm, large site with over 100K nodes).
These are all cached pages (tried both Database and Memcache) using Page cache for anonymous users. Why is it taking 4 times more longer for Drupal to serve cached HTML of a term page versus cached HTML of a node page?
I am really stumped. Only time this changes is when I restart the Php-fpm. For a few minutes, term pages are close to 300ms before going back to 700+ms in few minutes.
Any ideas on what could be causing this? Could it be a php configuration issue?