Speeding up the background tasks
Add 4 cronjobs to run every minute but prefix them with "sleep 0 && ", "sleep 15 && ", "sleep 30 && ", "sleep 45 && ".
This significantly increased the speed of the background tasks on our board.
Depending on your server setup you could increase or decrease the amount of cronjobs and associated sleep values (6 cronjobs => sleep 0, 10, 20, 30, 40, 50).