Database
[{"_id":1,"people":[{"name":"Jhon Smith","age":"30","state":"NY"},{"name":"Clint Mercer","age":"50","state":"NY"},{"name":"Walter Smith","age":"40","state":"WI"}]}]
Query
db.collection.aggregate([{"$match":{"_id":1}},{"$addFields":{"firstSmith":{"$arrayElemAt":[{"$filter":{"input":"$people","cond":{"$regexMatch":{"input":"$$this.name","regex":"Smith"}}}},0]}}}])