db={"users":[{"User":{id:"1",phone:"111 111 111",login:"abc"},"Address":{street:"Street",town:"NY"}},{"User":{id:"2",phone:"222 222 222",login:"xyz"},"Address":{street:"Street",town:"NY"}}],"updates":[{"User":{id:"1"},"Address":{town:"LA"}}]}

db.users.aggregate([{$match:{"User.id":"1"}},{$lookup:{from:"updates",localField:"User.id",foreignField:"User.id",as:"updatesLookup"}},{"$unwind":{path:"$updatesLookup",preserveNullAndEmptyArrays:true}},{"$replaceRoot":{"newRoot":{"$mergeObjects":["$$ROOT","$updatesLookup",{User:{"$mergeObjects":["$User","$updatesLookup.User"]}}]}}},{$unset:"updatesLookup"}])