Start by clarifying requirements and scale, then explain the core consistent hashing algorithm with a ring and virtual nodes. Walk through the API design, hash function choice, and node addition/removal handling, emphasizing minimal key movement and trade-offs.
Pro tip: Quantify the improvement: with V virtual nodes per physical node, adding/removing a node moves only ~1/(N+1) of keys, and V reduces load variance to ~1/sqrt(V). Mention real-world systems like DynamoDB and Cassandra to show practical awareness.
Ask about scale (number of keys, nodes), read/write patterns, consistency needs, and whether the system must handle node failures. This shows you avoid premature design.
Describe the hash ring: map nodes and keys to a circular hash space, assign each key to the first node clockwise. Highlight that this minimizes key movement when nodes join/leave.
Define operations like addNode, removeNode, getNode(key), and optionally getNodes(key, count) for replication. Use a sorted map (e.g., TreeMap) for the ring and a hash function like MD5 or SHA-1 for uniform distribution.
Explain that each physical node is represented by multiple virtual nodes (e.g., 100-1000) to improve load balancing and reduce variance. Discuss trade-offs: more vnodes = better balance but more memory and lookup overhead.
When a node is added, only keys that map to its vnodes move from the next clockwise nodes. When removed, its keys move to the next nodes. Discuss replication, failure detection, and consistency vs. availability trade-offs.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.