I've personally written grids that update in real-time and handle millions of updates over the course of a day. The stack was based on React as the frontend, we

I've personally written grids that update in real-time and handle millions of updates over the course of a day. The stack was based on React as the frontend, websockets as the delivery mechanism and Java on the backend and it scaled fine. So, IMHO, it's mostly a bad architecture or a sub-optimal design