If I understand this correctly, the only way to handle a player inviting a friend to a game (when cross-platform) is to create a room with your ID, toss the friend's ID in your player data and make it so all idle players periodically (every 3-5 seconds?) poll all of their friends' data and see if they find their own ID listed, and if so, offer the opportunity to join that room and start the match. Push notifications aren't an option in a cross-platform situation and users aren't allowed to post data in other user's file so, as far as I know, this is the only approach. Is this correct?