I have a MongoDB replica set with Three members: primary, secondary and hidden secondary, only for backups. Ideally, I want to add additional instance dedicated to running slow batch operations. The idea is to have this instance run map-reduce style operations which may take very long time to complete, without slowing down the regular queries which are required to finish quickly.
I am not aware of a Mongo configuration that can achieve this. I would love to hear ideas how to handle heavy, offline requests without affecting short, near real time requests.