Database
[{"_id":ObjectId("60994d48b223f7553c082ab2"),"name":"name","stateHistory":[{"state":"scanning","date":ISODate("2021-05-10T17:13:44.238Z")}],"__v":0}]
Query
db.collection.aggregate([{$addFields:{maxState:{$arrayElemAt:["$stateHistory.state",{$indexOfArray:["$stateHistory.date",{$max:"$stateHistory.date"}]}]}}}])