This is the kind of question where you think you know it cold and then you open your mouth and realize you've been fuzzy on the details for years.
Start by clarifying requirements (scale, consistency, latency, eviction policy) and then propose a high-level architecture with a distributed cache layer, consistent hashing for partitioning, and replication for fault tolerance. Dive into the LRU eviction mechanism per node, discuss trade-offs between local and global LRU, and address consistency and failure handling.
Pro tip: Emphasize that a true global LRU is impractical in a distributed system due to coordination overhead; instead, propose a per-node LRU with a consistent hashing ring and discuss how to approximate global LRU using techniques like segmented LRU or frequency-based admission.
Ask about expected scale (QPS, data size), latency requirements, consistency needs (strong vs eventual), and eviction policy specifics (strict LRU vs approximate).
Propose a distributed cache cluster with consistent hashing to partition keys across nodes, and replication for fault tolerance. Mention a coordinator or client-side hashing for routing.
Describe how each node implements LRU using a hash map and doubly linked list, and discuss concurrency control (e.g., sharding within a node, locks, or lock-free approaches).
Explain how eviction works across nodes: per-node LRU vs global LRU trade-offs. Discuss cache coherence, replication strategies (e.g., primary-backup), and how to handle node failures (e.g., rebalancing).
Discuss trade-offs: memory overhead, latency vs consistency, and potential optimizations like segmented LRU, TTL, or write-through/write-back policies.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.