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.
Functional requirement:
Scale requirement:
How many users are there?
How many times does a user interact with content (listens to a song)?
How many times does a user request top k?
How long should the raw data be retained?