Not a very helpful answer but in my experience, backend workflows are by nature slooowwww and it’s just a “feature” you have to live with. It’s kind of difficult to comprehend that generally, databases deal with 1000-10000 inserts per second, Bubble does 1-5 inserts per second. So if your problem is bulk loading of data quickly - Bubble will never be a great solution.
The best place I’ve got to with Bubble is to schedule “batches” of say 200 units of processing every hour, and schedule it to run over 12 hours. (because of silent process death with long-running processes in Bubble)
My suggestion would be for those tables that have a lot of records that you need to load and unload quickly - use an external database for those records - @jared.gibb has done this successfully with Firebase.
On the plus side, I’ve not seen a backend workflow impact the runtime performance of the frontend Bubble App.
eg this sort of stuff…
http://forum.bubble.io/t/is-there-a-limit-on-how-many-records-can-be-processed-at-once/174338/8