WARNING: the following is geeky devops/sysadmin stuff that has nothing to do with keto.
I moved servers quite recently and in the process went from Apache to Nginx. Nginx is indeed much faster but it has come with a pretty steep learning curve to get everything working right. And today I ran into a problem with non-logged in (guest) users getting scrambled or lost shopping carts. Seems to be the “microcaching” that was messing things up. I’ve removed that and it seems to be working much better. Memcached is still going but just for wordpress “transients” and not sessions. I’ll see if I can reenable those later. Sort of reminds me of this GIF from devopsreactions.
Let me know if you experience any weirdness.