This is related to javascript stored function in mongodb server. I know all the details about the working and use cases. I am doubtful about one line which is in the official documentation of MongoDB.

"Note : We do not recommend using server-side stored functions if possible."

After moving to V8 JavaScript engine ( improving concurrency issues for javascript queries ) and given the fact this may save us many network round trip time, why this is not recommended?

Also, if there some performance difference in running javascript queries Vs running normal queries ( given both are able to use index ) ?

Please link me to supported documentation. Also, it will be much useful, if the reason for such statements are also mentioned in the documentation.