An interesting tidbit is that some of the picking processes described in the video I linked to above were implemented only recently as COVID-19 simultaneously applied upward pressure on order volume (people shopping online more) and downward pressure on fulfillment capacity (warehouse worker density restrictions). We literally had to stop taking orders for a short while to keep the backlog of orders reasonable.
It was gratifying to apply things we learned from computer science and industrial engineering together to help us keep up with demand.
I used JQuery Mobile for the mobile version of our site. Performance is definitely an issue. I believe that it will eventually improve with future versions so I stuck with it and used just a subset of the features that had acceptable performance. The compromise in performance was worth not having to worry about cross-device compatibility.
Specific performance issues I ran into:
1) The page transitions were too slow so I didn't use them at all and instead just do page reloads for everything.
https://github.com/jquery/jquery-mobile/issues/3217