Popular articles cache
Design a read cache in front of a database for a small site whose home page shows the 'top 10 most popular articles'. Computing that list is a moderately expensive query, the home page is the most-visited page, and the ranking only needs to update every few minutes. Describe how you cache the result and keep it reasonably fresh.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify3:00 left
Estimate3:00 planned
Design8:30 planned
Deep dive6:30 planned
Failure4:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.