Time Based Key-Value Store
Part 1: Simple Cache - set(key, value): store a value - get(key): return value for key, or "" if missing
Each key holds multiple values at different timestamps, and you need the most recent value at or before a given time. Interviewers love it because it reveals your binary search precision—one wrong boundary update can loop forever. The trap is boundary drift. Nail this and temporal queries become second nature.
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