we have weird issue: Checkout ttfb after refreshing cache is about 5 seconds When we leave site going (production mode, visitors visiting) after day we get to loading time up to 20 seconds, when even more we get times more than 40-50s ttfb. When one cache is refreshed, time of ttfb will reduce back to "normal" . For now we refresh one cache, that is even disabled to keep loading times bearable. Regular ttfb for cached page (with FPC,ssl) is under 0,3s
Running on VPS with 4x CPU and 4GB ram.
Magento with 4 storeviews 18.104.22.168
Debian with php 5.6.33
+we had tested different checkouts including magento's default, results in same loading times.
Edit: uploaded profiler pics
•product page without cache: https://i.stack.imgur.com/eCiTJ.jpg
•checkout with 12hours old cache https://i.stack.imgur.com/nSEm3.jpg
• checkout with refreshed cache https://i.stack.imgur.com/0zCTP.jpg