db={user:[{"_id":2,"counterParty":2,"email":"some@root","password":"bad","status":"I am new",},{"_id":3,"counterParty":1,"email":"some@root","password":"good","status":"I am beginner",},{"_id":1,"counterParty":2,"email":"someother@root","password":"verygood","status":"I am expert",},],CounterParty:[{_id:1,name:"John"},{_id:2,name:"Jenny"}]}

db.user.aggregate([{$match:{email:"some@root"}},{"$lookup":{from:"CounterParty",localField:"counterParty",foreignField:"_id",as:"details"}}])