How does Railgun work?
Railgun opens a secure tunnel connection between the CloudFlare network servers and your host’s origin server where the connection only sends differences from the last request.
The markup of websites does not change that frequently from one request to the next. Instead of transferring the entire request between CloudFlare and the origin server, Railgun will transfer only the changes in markup from one request to the next so this cuts down on bandwidth, transfer time, and overall page load times.
Railgun caches these differences in its memory to make page processing times as fast as possible.