[{"result":{"events":[{"amount":[[1623224700000,"33333333"],[1623224760000,"33333333"],[1623224820000,"33333334"]],}],}}]

db.collection.aggregate([{$set:{"amount_sum":{$sum:{$first:{$map:{input:"$result.events",as:"event",in:{$map:{input:"$$event.amount",as:"amount",in:{$toInt:{$last:"$$amount"}}}}}}}}}}])