Good to know that you were able to manage this issue.
FYI, ATUM itself is not heavy. Just that, in order to calculate some sales props, if your database is big (thousands of orders), the SQL queries that are needed for such calculations can take time to run. That's why a big part of these calculations are scheduled at night and run in the background. So, sometimes, it's just a kind of adjusting the server to your needs (mainly the resources handled by the MySQL server according to the size of your database).