The problem had a lot of moving parts and I kept second-guessing myself on the tie-breaking rule.
Start by clarifying requirements and constraints, then outline the data structures: a sorted array or balanced BST of virtual node hashes, each mapped to a shard. Explain the custom 32-bit FNV-1a hash function, how virtual nodes improve load balancing, and how routing uses binary search to find the nearest clockwise node. Finally, discuss trade-offs like replication factor, virtual node count, and handling shard removal.
Pro tip: Mention that virtual nodes should be distributed using a deterministic hash of shard ID + replica index to avoid collisions and ensure even distribution. Also, note that using a sorted array with binary search gives O(log N) lookup, but for very large rings, a balanced BST or skip list may be better for dynamic updates.
Ask about expected number of shards, keys, read/write patterns, and whether the ring must be persistent or in-memory. Confirm the need for virtual nodes and the custom hash function.
Propose a sorted collection (e.g., array or balanced BST) of virtual node hashes, each storing a reference to its shard. Explain how to generate virtual nodes by hashing shard ID + replica index.
Describe the 32-bit FNV-1a algorithm: initialize hash to 2166136261, then for each byte, XOR with the byte and multiply by 16777619. Ensure it handles strings and is deterministic.
For routing, hash the key and binary search for the first virtual node hash >= key hash (wrapping around). For adding/removing shards, insert/delete all virtual nodes for that shard and optionally rebalance keys.
Cover trade-offs: number of virtual nodes vs. memory, lookup complexity, rebalancing cost, and alternatives like consistent hashing with bounded loads. Mention potential hot spots and mitigation.
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