How to improve TTFB

My TTFB is 1.9 second
LSCache is enabled and Memcache is enable
I want to improve TTFB speed
Please let me know how to improve this
I'm having the same problem. My site is not hooked up on Cloudflare though. I realized their HTTP/2.0 headers slow down the TTFB and the only way to deactivate HTTP/2.0 on Cloudflare you have to upgrade to PRO.

However, I was using CentOS Web Panel to manage my site. I had to do a lot of DIYs and it enabled my site to have a TTFB of less than 200ms. On OpenLiteSpeed, however, I have tried everything and the TTFB is still terrible. Hovers over 600ms