System design interview question
"Design a distributed LRU cache. Start with the single-node data structure — I want to see the exact mechanics of O(1) get and put with LRU eviction — and then extend it across a cluster. Tell me what 'LRU' even means when the cache is spread over a hundred machines."
A hybrid question — a classic data-structures problem (hash map plus doubly linked list) followed by the systems question of what happens to that structure when distributed. The best signal is whether the candidate recognizes that a globally correct LRU across a cluster is impractical, and that the real design is per-node LRU with a routing layer.
On Practick another engineer interviews you live for 60 minutes on a question from this bank. They have the full interviewer guide beside the call: the answers to your clarifying questions, the numbers to hand out, a ladder of follow-ups and a scoring rubric. You get the model solution once the session settles. It is free: interview someone for an hour and you have earned your own.
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