[{"_id":1,"rides":[{"status_history":["status1","status2","status3"]},{"status_history":["status4","status5"]}]}]

db.collection.update({},[{"$set":{"size":{"$size":"$rides"}}},{"$set":{"rides":{"$concatArrays":[{"$cond":[{"$gt":["$size",1]},{"$slice":["$rides",0,{"$subtract":["$size",1]}]},[]]},[{"status_history":{"$concatArrays":[{"$cond":[{"$gt":["$size",0]},{"$arrayElemAt":["$rides.status_history",{"$subtract":["$size",1]}]},[]]},["new-status"]]}}]]}}},{"$unset":["size"]}])