I have been searching for the reason why the Response to Server (TTFB) has some major delays on:
https://tools.pingdom.com/#!/cu9yoV/https://graphic-cv.com
without finding the real reason. It resides on a shared server which in fact is running with good hardware and the site is running PHP 7.1, APCu cache, Cloudflare, PrestaShop 1.6.1.18 platform configured with the best speed optimization setting in the backend
As seen on the metrix test the site requests are loading within seconds, but the first http/https request to the server can delay the site all from 3 seconds to 20 seconds. If I do a re-test it will go down to 2-5 seconds, but if I haven't accessed the site 30 min and up, issues will arise again with high load time.
How do I find the culprit which is delaying the TTFB? The hosting company with all their resources for testing/monitoring haven't provided me with a clear answer.
It was hardware related. After the hosting company upgraded their hardware, new CPUs, RAID-10, DDR4, Litespeed, now my site loads within 3 seconds.