It comes down to whether you're going to dominate node's thread or not, if it's heavy or of course blocking then you'll have to do push that work off to be handled by a different thread.
In my case I periodically query mongodb for new or updated data since the last time to be stored locally, push batches of data into redis, track and save load information etc all without any negative repercussions.
In my case I periodically query mongodb for new or updated data since the last time to be stored locally, push batches of data into redis, track and save load information etc all without any negative repercussions.