Hello @Rafael Gil Sanchez ,
Thanks for reaching Microsoft Q and A platform.
How Frontdoor works:
· Azure Front Door delivers your content using Microsoft’s global edge network with hundreds of global and local points of presence (PoPs) distributed around the world close to both your enterprise and consumer end users.
· The user or client application initiates a connection to the Front Door. The connection terminates at an edge location closest to the end user. Front Door's edge location processes the request.
· Edge Location will have the POP servers, where the request would cache if enabled the cache without request been sent all the way to “Origin” which is added as the backend in the Frontdoor config.
· How to know your request hit which POP server:
Once you enable the Diagnostics log in the Frontdoor and see the request, you will have the information on which POP server and location the request hit on, which indeed is the Edge Location.
Now, this could explain what does the Data Transfer out and Data Transfer in means. 😊
In simple: Client ==> AFD (Nearest POP), if cache return data to client (If not) ==> Pull the data from Origin.