Design a Crash-Resilient LRU Cache
Company: Anthropic
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Technical Screen
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.
Quick Answer: 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.