Top Songs: Return Top-K Most Played Songs Per User

Problem You are given a list of play events (user_id, song_id). For each user, return the top k most-played songs (by play count), breaking ties by song_id ascending. Return a dictionary mapping each user to their ranked list. Follow-ups How would you use a heap to get top-k without fully sorting the song list per user? If the event stream is very large (billions of entries), how would you compute this with a distributed map-reduce approach? How would you handle a sliding window: top-k songs pla…