How can CDN impact TTFB ?

[dfavor]

Best to test your exact setup.

Many times CDNs provide very minor speed ups (the global backbones are very fast now) with massive amounts of caching problem headaches.

When I take on new private hosting clients, my first step is always to strip out any cruft between an Apache server + a visitors browser.

All cruft - load balancers, DOS mitigators, CDNs, proxies (NGINX, Squid, Varnish), session caches (memcached).

Then just tune the LAMP Stack for speed.

I have some servers (hosting WordPress sites) which have been running 250K requests/hour, sustained for years. Average CPU usage is 1/2 of on CPU load unit + very little Disk I/O.

This is all accomplished through LAMP Stack tuning.

Best to focus on tuning your Stack first. Likely this will sufficient.