[{"certnumber":"123456","createtime":ISODate("2024-02-03T16:42:20.324Z"),"company":"A"},{"certnumber":"123456","createtime":ISODate("2024-02-03T16:32:20.324Z"),"company":"A"},{"certnumber":"123456","createtime":ISODate("2024-02-02T14:28:20.324Z"),"company":"A"},{"certnumber":"123456","createtime":ISODate("2024-02-02T13:22:20.324Z"),"company":"A"},{"certnumber":"654321","createtime":ISODate("2024-02-05T17:42:20.324Z"),"company":"B"},{"certnumber":"654321","createtime":ISODate("2024-02-05T16:42:20.324Z"),"company":"B"},{"certnumber":"654321","createtime":ISODate("2024-02-03T15:32:20.324Z"),"company":"B"},{"certnumber":"654321","createtime":ISODate("2024-02-03T14:22:20.324Z"),"company":"B"}]

db.collection.aggregate([{"$sort":{"certnumber":1,"createtime":1}},{"$group":{"_id":"$certnumber","lastDoc":{"$last":"$$ROOT"}}},{"$replaceRoot":{"newRoot":"$lastDoc"}},{"$merge":{"into":"collection2"}}])