Nginx cache shared between multiple servers

There seems to be a rather new blog post at https://www.nginx.com/blog/shared-caches-nginx-plus-cache-clusters-part-1/ about this issue. This first example could be usefull if you run more than two nginx cache servers.

Especially the second part of the post sounds interesting for my current use-case, where I want to automatically re-crawl changed items into my caches.

It should work with the open source Version of NGINX too. Basically it works by proxying the request cascaded through each NGINX Server (Nginx-Cache1->NGinx-Cache2->Origin-Server) each server caches from the relevant upstream and if desired it is possible to create a HA Cluster too. https://www.nginx.com/blog/shared-caches-nginx-plus-cache-clusters-part-2/