Design feed ranking
Medium45 minFree, no account
The label is the hard part, and optimising the obvious one makes the product worse.
The question
Design the ranking system for a social feed: given a user and a few thousand candidate posts, order them.
Be explicit about what you are predicting and what success means.
Functional
- Rank candidates for a user in a single request.
- Blend several objectives, not just one.
- Handle new posts and new users with no history.
Non-functional
- Ranking under 100ms for ~1,000 candidates.
- Model refreshed at least daily; features fresher than that.
45:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.
Stuck?
0 of 3 hints takenThe worked solution
written by a person · not a gradeScore yourself
0 of 5 marked- Stated the prediction unit and target precisely20
- Interrogated the label and rejected naive click optimisation25
- Two-stage architecture justified by latency20
- Named position and exposure bias with a concrete correction25
- Handled the three cold starts separately10
We run no AI here and nothing on this page grades you. The score is yours, and the useful number is the one you get on the same problem a month from now, cold.
kept in this browser only