Started with the basics: a hashmap storing value plus expiry timestamp, check on get and return null if stale.
Start by clarifying requirements (e.g., expected scale, consistency needs, TTL precision) and then design a basic in-memory key-value store with per-key TTL using a hash map and a min-heap or timing wheel for expiration. Discuss eviction strategies like LRU or LFU, thread-safety via sharding and locks or lock-free structures, and scaling through consistent hashing and replication. Conclude by addressing trade-offs and potential bottlenecks.
Pro tip: Emphasize that TTL expiration should be lazy (on access) combined with active background sweeping to balance accuracy and performance, and mention that Netflix often deals with high-throughput, low-latency systems, so consider using off-heap memory or a distributed cache like EVCache.
Ask about expected throughput, latency, data size, TTL precision, consistency, and persistence needs to tailor the design.
Propose a hash map for key-value storage and a separate structure (e.g., min-heap, timing wheel, or sorted set) to track expiration times efficiently.
Explain how to handle expired keys (lazy deletion on access plus periodic sweeping) and eviction when capacity is reached (e.g., LRU, LFU, or TTL-based).
Discuss locking strategies (e.g., fine-grained locks, read-write locks), sharding to reduce contention, or lock-free approaches using atomic operations.
Describe horizontal scaling via sharding (consistent hashing), replication for fault tolerance, and potential use of a distributed cache layer.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.