Database / ScyllaDB Interview questions
How does ScyllaDB achieve linear scalability per node?
Per-node scalability in ScyllaDB comes from combining the shard-per-core architecture with a design that avoids shared, contended state as core counts grow. Each core runs its own shard with its own memtable, cache, and connections, so adding cores adds independent capacity rather than more contention on a single shared structure.
Cross-shard communication happens through explicit, asynchronous message passing rather than shared-memory locks, which keeps the cost of coordination bounded and predictable even as core count rises. This is why doubling a node's CPU cores in ScyllaDB tends to roughly double its achievable throughput, a property that's much harder to guarantee in a JVM-based database where garbage collection and lock contention scale poorly with thread count. At the cluster level, this per-node scalability compounds with horizontal scaling across nodes via consistent hashing, giving both dimensions of scale.
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