I ran across this presentation with Amazing Info on how Scalable LXC/LXD is from MARS project (Petabytes Data Migration and Load Balancing with Football+MARS) Multiversion Asynchronous Replicated Storage by Thomas Schöbel-Theuer (tst@1und1.de)
It was presented at linux.conf.au Feb 9th 2019 and I posted the info you can read/watch about it on the LXD subreddit: