Two different things people confuse.
SERVER-SIDE CACHING
Stores generated pages on our server. A cached page is served without running your application.
That reduces CPU, memory and database load on your account directly.
CDN CACHING
Stores files at locations around the world. A cached file is served without reaching our server at all.
That reduces bandwidth and improves delivery distance.
WHICH TO DO FIRST
Server-side caching. It addresses resource limits, page generation time and database load.
It is also free, already available through LiteSpeed, and understands your application's exclusions.
WHERE A CDN ADDS TO IT
Serving assets closer to distant visitors Absorbing traffic spikes Filtering bad traffic, where the CDN offers it
WHAT NEITHER FIXES
A site with four megabyte images. Caching an oversized file delivers it faster and does not make it smaller.
THE COMMON MISTAKE
Adding a CDN to fix slowness while server-side caching is off.
Check caching first, always.