That's not a Meteor issue. Running aggregations on fact tables at runtime is slow. On top of that, being a document store, mongo is not the best at aggregations

That's not a Meteor issue. Running aggregations on fact tables at runtime is slow. On top of that, being a document store, mongo is not the best at aggregations. Then instead of using mongo you use minimogo (DB implemented in JS). Then you rerun that query all the time. Of course it'll be slow/expensive. :)