We use dataflows to load analytical (not CDS) tables to be consumed by PowerBI reports for multiple of our clients.
On initial setup, the speed (few seconds to minutes) was impressive, especially after suffering many implementations loading CDS tables, which would take hours to load.
In the last few days, we are now back to poor performance! It's really working within the environment thats slow. Just opening the dataflow, editing, and saving the change takes many minutes. I create a new dataflow, save, and refresh the page and it still does not show up. I can try to recreate the same dataflow (using same name) and it reopens the prior queries. Even tho this dataflow has not yet appeared in the 'My Dataflows' list.
We have 2 different clients, and both logins/environments have the same slowness issues?