What is the purpose of virtual nodes in a hash ring?

• A. They assign multiple positions on the hash ring to each physical node to improve load distribution.
• B. They reduce the need for a hash function entirely.
• C. They ensure a single node can handle all traffic indefinitely.
• D. They guarantee identical traffic for all keys.

Answer: (A)

The idea being tested is how virtual nodes help balance load in a consistent hashing setup. In a hash ring, keys are hashed to points on a circle and served by the next node clockwise. If each physical node has only one position on the ring, the distribution of keys can be quite uneven, especially as nodes come and go or if nodes have different capacities. Assigning multiple positions on the ring to each physical node—creating many virtual nodes—spreads keys across many more points. This smooths the load, reducing hotspots and making the system more predictable under churn. It also makes scaling and rebalancing cheaper: when a node is added or removed, only the keys mapped to its virtual positions need to migrate, rather than rehoming a large portion of the ring. So, virtual nodes exist to improve load distribution and resilience. The other statements don’t fit: the hash function is still needed, virtual nodes don’t force a single node to handle all traffic, and they don’t guarantee identical traffic for all keys.