Your question is Time Series Database. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design a time series database.
This was asked in the Onsite stage. Discuss the storage model, ingestion path, query execution, retention, scaling, and failure handling. Treat the exercise as a practical system design problem and state reasonable assumptions where requirements are unspecified.