end users computer is the bottleneck. cpu single thread performance is the limiting factor as far as i can tell. also different versions run faster. im on 1.2.12 - i think that was fastest up to 1.2.19 when .19 was most current. also i believe Chrome was the fastest at that time. we run one board, usually average 300+ tasks (7 swimlanes, 20+ columns), ubuntu/mysql backend in house virtual server. right now at 199 tasks (tasks expanded, no horizontal scrolling = full board view of all tasks) and refresh on board is 1.65s with i3-12100 (3488 single thread rating). drag and drop in same time frame. i have other computers with much higher rated cpu multithreaded scores (but lower single thread scores) that are slower. this applies to ipads/phones i tested - high single thread performance is always better.