Your question is Design an LFU Cache. 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 Least Frequently Used Cache, with an optimal cache design solution.
Asked in the Round 2 - face-to-face technical stage. One of three problems to code optimally within one hour.
Explain the data structures and invariants, then implement the cache with constant-time get and put operations. Define how ties between equally frequent entries are resolved, how updates affect frequency, and how zero-capacity caches behave. Discuss time and space complexity and the edge cases you would test.