Database
[{_id:"123",status:"seen",userId:"589"},{_id:"223",status:"seen",userId:"589"},{_id:"474",status:"unseen",userId:"589"},{_id:"875",status:"seen",userId:"112"},{_id:"891",status:"unseen",userId:"112"}]
Query
db.collection.aggregate([{$facet:{totalNumOfSeen:[{$match:{userId:"589",status:"seen"}},{$group:{_id:"$userId",totalNumOfSeen:{$sum:1}}}],totalNumOfNoticationsSent:[{$match:{userId:"589",}},{$group:{_id:"$userId",totalNumOfNoticationsSent:{$sum:1}}}]}}])