Design a single-node persistent in-memory cache

Scenario

Design a single-machine cache used by a web service to handle read/write requests.

The cache should:

• Store key/value pairs in memory (fast reads)
• Support typical operations: Get(key) , Put(key, value) , Delete(key)
• Enforce an eviction policy such as LRU when memory capacity is reached
• Optionally provide durability so that after a process crash/restart, the cache can recover its contents

The interviewer expects:

• A concrete design with data structures
• Pseudocode-level APIs and key internal logic
• Discussion of concurrency (locks), minimizing critical sections, avoiding deadlocks
• How to scale on a single machine (e.g., sharding/striping to reduce lock contention)