Plug in your rekordbox USB. The booth reads it like a player: playlists, tag list, hot cues, memory cues, beat grids, colours and keys. rekordbox XML or a folder of files works the same way.
Unanalysed tracks are analysed on load: tempo, beat grid, key, waveform. MP3, AAC, WAV, AIFF, FLAC and OGG. Nothing is uploaded.