[{"_id":1,"price_history":[{"date":"10 - 01 - 19","price":10},{"date":"10 - 05 - 19","price":15}]},{"_id":2,"price_history":[{"date":"10 - 01 - 19","price":12},{"date":"10 - 05 - 19","price":14}]},{"_id":3,"price_history":[{"date":"10 - 01 - 19","price":17},{"date":"10 - 05 - 19","price":25}]},{"_id":4,"price_history":[{"date":"10 - 01 - 19","price":10},{"date":"10 - 05 - 19","price":16}]}]

db.collection.aggregate([{$unwind:"$price_history"},{$sort:{"price_history.price":1}},{$group:{_id:"$_id",price_history:{$last:"$price_history"}}}])