Custom VCL

You want to try out multiple variations of a page or a feature of your website, dividing your users into groups, some of whom experience one version, and some the other. Once a person is in one group, they should continue to get a consistent experience.

Your website includes JavaScript on the client side that generates analytics, and you want to collect this data, but want to avoid an uncacheable request reaching your servers for every page view. Fastly's real-time logging can help.

The popular JSON Web Token format is a useful way to maintain authentication state and synchronize it between client and server. You are using JWTs as part of your authentication process and you want to decode and validate the tokens at the edge, so that content can be cached efficiently for all authentication states.

Your servers often have to handle millions of requests for old and non-canonical URLs. This can cause unneeded load, as well as make logs messier and, if you have recently changed your site's URL scheme, you might be redirecting a lot! Learn how to shift all your static redirects to the edge using a dictionary.

To help debug issues and monitor backend behavior, you can capture and log the origin server's name, IP, and port, ensuring visibility into where requests are routed, even when responses aren't cached.