Duplicates can be submitted when both Spotify and LB Android submit a listen. To tackle this, the app can show a popup to user when it detects so. How to detect? Solutions:

1) Simplest solution might be to just look at latest LB Android and Spotify submission with a fixed timestamp difference that is to be hardcoded. How to "look"? Use artist, release_name, media_player and submission_client to do so.