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LRU Cache
Design a cache that evicts the least recently used item when full. It's one of the few problems that tests both data structure intuition and clean API design. Interviewers love it because it reveals whether you can combine a hash map with a linked list to get O(1) operations. This pattern shows up constantly in systems design.
Learn this pattern
Low-Level Design Interview Questions
Low-level design problems test whether you can model a small API, preserve invariants, and choose storage that matches the required operations. Expect recurring shapes like rate limiters, hit counters, tic-tac-toe, file systems, and autocomplete.
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