I built my own CDN with Varnish and Nginx

I ran dozens of sites, some with significant traffic, off of 3 servers for years: a DB server, a web app server, and a server running Nginx and Varnish. All in a single data center.

Tuning the cache was a way better use of my time than trying to place copies in data centers overseas. A site has to be pretty darn fast to see a significant improvement from geographic dispersal alone. Most of the value people get from Cloudflare or Fastly is the caching, not geography.

But the downside of DIY is you have to do it yourself, including Linux sysadmin. Which is one reason we don’t do it that way anymore.