Mastering LRU Cache: Shopify's Challenging Tech Interview Round

Software Engineering
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shopify | | Interview Experience

Interview Date: Not specified
Result: Not specified
Difficulty: Not specified

Interview Process

The interview focused on designing and implementing a Least Recently Used (LRU) Cache. The candidate was asked to explain the concept and the requirements for the implementation. The process included discussing the functional requirements, eviction policy, and the rules for keys and values.

Technical Questions

  • Implement an LRU Cache
    • Discussed functional requirements:
      • CRUD Operations: write(key, value), read(key), delete(key), clear(), count(), to_h()
      • Eviction Policy: Automatically remove the least recently used item when capacity is exceeded.
      • Key and Value Rules: Keys must be hashable; empty strings are valid keys; values can be any object.
      • Return Semantics: read() returns cached value or None; delete() returns removed value or None; clear() returns the number of cleared entries.

Tips & Insights

Focus on the efficiency of operations (O(1)) and discuss considerations for concurrency, logging, and scalability during the implementation.