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hardAnthropic

Extend an LRU cache to key on *args and **kwargs, then make it persistent across restarts

Anthropic's reported twist on the LRU staple: the cache is a decorator, the keys are arbitrary call signatures, and the follow-up writes it to disk. The kwargs-ordering and unhashable-argument traps are the whole interview.

Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

Anthropic's reported twist on the LRU staple: the cache is a decorator, the keys are arbitrary call signatures, and the follow-up writes it to disk. The kwargs-ordering and unhashable-argument traps are the whole interview.

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