[{"_id":"0001","Name":"John","Contacts":[{"Person":[{"User":{"_id":ObjectId("5836b916885383034437d230"),"Name":"Name1","Age":25}},{"User":{"_id":ObjectId("2836b916885383034437d230"),"Name":"Name2","Age":30}},{"User":{"_id":ObjectId("1835b916885383034437d230"),"Name":"Name3","Age":31}}]}]}]

db.collection.aggregate([{"$match":{"Contacts.Person.User.Age":{"$gte":30}}},{"$unwind":"$Contacts"},{"$unwind":"$Contacts.Person"},{"$match":{"Contacts.Person.User.Age":{"$gte":30}}},{"$project":{"_id":"$Name","ContactName":"$Contacts.Person.User.Name","Age":"$Contacts.Person.User.Age"}}])