I believe only in behavioural "biometrics" which combines knowledge and inference together with zero knowledge proof to locally authenticate users on their personal and probably secure devices. Any other attempts in using biometrics are futile.
I would argue that they store the coins in the custody vault as close to the exchange point as possible so the fast transfers are frictionless...and that would cost a premium.
One tool I wrote and I wish I would still have time to maintain was "Folders2Flickr" (luckily someone forked it https://github.com/richq/folders2flickr and keeps it alive). It's basically a DropBox for pictures with Flickr being the storage server and viewer. The tool simply synchronizes all of your pictures which can be in a hierarchical folder structure and recreates this folder structure on Flickr (but uses Sets/Albums instead of folders). I dont see the stats now but for years it supplied Flickr with multiple pictures every single second 24/7 from many users.