[{id:"ran1",code:"ABC1",createdAt:"Sep 1 2022",count:5},{id:"ran2",code:"ABC1",createdAt:"Sep 2 2022",count:3},{id:"ran3",code:"ABC2",createdAt:"Sep 1 2022",count:2},{id:"ran4",code:"ABC1",createdAt:"Oct 1 2022",count:1},{id:"ran5",code:"ABC1",createdAt:"Oct 2 2022",count:2},{id:"ran6",code:"ABC2",createdAt:"Oct 1 2022",count:1},]

db.collection.aggregate([{$addFields:{month:{$month:{$toDate:"$createdAt"}}}},{$match:{month:10}},{$group:{_id:{code:"$code"},count:{$sum:"$count"}}}])