I have a requirement for a web application in the following things happens

1 user upload audio files to the web server

2 web server reads the metadata(duration, bit rate,format,channel count etc...) & reduce the bit rate of those files and stores in a persistent storage.

This app got high scalable scope and I need to develop a system in such a way that it should be able to do the audio files conversion concurrently to a large number of users.Can somebody suggest good tech stacks to do it.

I was thinking about to use nodejs for api app and python for media processing along with mongodb database.Can anybody suggest some cool libraries for this purpose???