Database
[{_id:1,"_a":[{"_aId":{"CC":"NL"},"_p":[{"_pId":{"CC":"NL"},"s":{"c":{"t":[{sId:1,language:"NL",format:"A4"},{sId:2,language:"JP",format:"A4"}]},"a":{"t":[{sId:4,language:"NL","format":"A4"},{sId:5,language:"EN","format":"A3"}]},"d":{"t":[{sId:10,language:"","format":"A4"}]}}}]}]}]
Query
db.collection.aggregate([{$match:{"_a._p._pId.CC":"NL"}},{$unwind:"$_a"},{$unwind:"$_a._p"}])