Database / ScyllaDB Interview questions
What is the difference between ScyllaDB tablets and vnodes?
| Vnodes (legacy) | Tablets (newer architecture) |
| Fixed number of token ranges assigned per node at join time. | Dynamically sized, independently balanced units of data per table. |
| Rebalancing after adding/removing a node can be slow and coarse-grained. | Rebalancing is finer-grained and much faster. |
| Manual tuning of vnode count sometimes needed for large clusters. | Automatically split and moved based on load, closer to Spanner-style splits. |
Vnodes were ScyllaDB's original approach, inherited from Cassandra's design, where each physical node owns many virtual token ranges to smooth out load distribution, but the granularity is still fixed once nodes join. Tablets are a newer, more dynamic model where each table's data is divided into independently-sized tablets that ScyllaDB can split, merge, and move much more responsively as load or cluster size changes, similar in spirit to how some distributed SQL systems handle splits, and they significantly speed up operations like adding a node or scaling a cluster.
Which architecture allows finer-grained, faster rebalancing?
Where did the vnodes approach originate?
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