Database
[{"_id":{"$oid":"fedcba9876543210fedcba98"},"at":ISODate("2022-03-25T05:00:00Z"),"productId":125},{"_id":{"$oid":"fedcba9876543210fedcba99"},"at":ISODate("2022-03-25T04:00:00Z"),"productId":125},{"_id":{"$oid":"fedcba9876543210fedcba9a"},"at":ISODate("2022-03-24T12:00:00Z"),"productId":126},{"_id":{"$oid":"fedcba9876543210fedcba9b"},"at":ISODate("2022-03-25T08:00:00Z"),"productId":127}]
Query
db.collection.aggregate([{"$match":{"productId":{"$in":[125,126]}}},{"$group":{"_id":"$productId","newRoot":{"$top":{"sortBy":{"at":-1},"output":"$$ROOT"}}}},{"$replaceWith":"$newRoot"}])