Design a Crash-Resilient LRU Cache

Q: Design a Crash-Resilient LRU Cache

This question evaluates a candidate's competency in designing a crash-resilient LRU cache, including which data and ordering must be persisted, durability and recovery concerns, and trade-offs between latency and persistence.

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Question

You have an in-memory LRU cache with fixed capacity and standard get(key) / put(key, value) operations. Normally, an LRU cache is volatile, but now you want the cache to recover useful state after a process crash or restart.

Design a persistence strategy for this cache.

Discuss:

What data must be persisted.
How to reconstruct both the key-value entries and the LRU ordering.
Whether to use snapshots, a write-ahead log, or both.
The trade-off between durability and latency.
How recovery should work after a crash.

Design a Crash-Resilient LRU Cache

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