Top K Heavy Hitter

For a platform like Spotify, design a sytem that returns the top K songs played in the last 7 days. The same solution can also be applied to getting the top K most popular items of an e-commerce platform.

• When a user plays a song, increment count for that song
• Return the top K songs played for the last 7 days

How many users are there?

• 100,000,000 DAU

How many times does a user interact with content (listens to a song)?

• 100 times a day.

How many times does a user request top k?

• 2 times a day for last 7 days

How long should the raw data be retained?

• Data retention for 1 year.