I have been working on speed ups for a large site running 5.6 and found the article discussing defining PAGE_CACHE_LIBRARY to use varnish as a full page cache.
I would be very interested in testing this is a new site I am working on using 8.1. Is this still possible? I have searched the forums and found a lot of discussions about speed enhancements and tuning. But nothing addressing this issue.

The alternative is to put Varnish in front of C5 which I am currently testing, and is giving me a vast speed improvement, both in time to first byte and page load times, but I want to leverage the caching even when users are logged in.Logins will be both admins and users. I also have caching running for ssl by terminating in nginx. I know that there is the logged in cookie issue which I am working through.

Any advice on implementing this approach would also be most appreciated.

Thanks
Martyn