[{"_id":1,"need_some":"A","need_more":1,"website_id":"123456789"},{"_id":2,"need_more":2,"website_id":"123456789"},{"_id":3,"website_id":"123456789"}]

db.collection.aggregate([{"$addFields":{"field":{"$objectToArray":"$$ROOT"}}},{"$match":{"field.k":{$regex:"need_"}}},{"$project":{"field":0}}])