CloudFlare is a very popular free CDN that acts as a reverse proxy to your website. CloudFlare was an unintended CDN in the fact that it works by sending your users through the CloudFlare system to see if they are a potential threat to your web site. However, in doing so it also acts a CDN as CloudFlare will serve a static version of your website which in turn reduces your load time, and cuts out a large amount of spam.
There are those who are quick to point out that if you are using a CDN then there is no point in using CloudFlare as this would be redundant and that CloudFlare does not cache all files on your website. While it is true that CloudFlare will not cache all your files it can still reduce spam, and the Rocket Loader feature can improve your load time as well. There are many websites that use both CloudFlare, as well as a CDN such as MAXCDN, and they have found that it improves their load time incredibly.
CloudFlare is a tool that is free for everyone, and it is included with many popular caching plugins including W3 Total Cache and WP Rocket. Here is an example website that is using CloudFlare, a CDN, and WP Rocket. By properly utilizing both free and paid tools, your website can load blazingly fast and be the envy of everyone else in your own Niche.