[{"history":[{/** "status": "Not Processed",*/"createdAt":{"$date":"2021-01-26T00:16:26.018Z"},"updatedAt":{"$date":"2021-01-26T00:16:26.018Z"}},{/** "status": "Processed",*/"updatedAt":{"$date":"2021-01-26T00:17:25.725Z"},"createdAt":{"$date":"2021-01-26T00:17:25.725Z"}}]}]

db.collection.aggregate([{$project:{"res":{"$reduce":{"input":"$history","initialValue":null,"in":{"$cond":{"if":{$and:[{$eq:["$$this.status","Processed"]},{$ne:["$$this.status",null]}]},"then":"$$this.createdAt","else":"$$value"}}}}}}])