SPECIALIf you use or plan to use a CDN
Setup can be a little complex
All security features offered by CDNs can be implemented locally so the decision to use a CDN should be based entirely on performance considerations and not security.
The Cloudflare CDN in particular, offers a free service that includes automatic filtering of traffic using spam block lists. This results in many legitimate users being presented with a CAPTCHA challenge.
Avoid CDNs like Cloudflare that use aggressive block lists. There are many other CDNs that will provide the improved performance without filtering your traffic.
My own experience with cloudflare
I have been presented with cloudflare challenges numerous times yet I never engage in any type of SPAM or hacking activities. I would seldom send more than 20 emails a day and never use any automated tools that would trigger the SPAM blocking. They do provide a way to request your IP be removed from their aggressive blocking list, but they do not make this easy. You need to search for the page to request removal, and then wait for them to respond and on more than a few occasions I have not received a response, and on others my request has been denied. I have given up. When I am presented with a captcha challenge now I am more inclined to just close the tab than enter their captchas.
https://www.cloudflare.com/features-security (not recommended)
This is a CND that does not use aggressive filtering: