There is an explanation for this. VoltDB latency is currently sub-millisecond for single-node deployments, but often several times higher for clusters. This is

There is an explanation for this. VoltDB latency is currently sub-millisecond for single-node deployments, but often several times higher for clusters. This is due to the current system of global-ordering-agreement that adds some latency. So for synchronous workloads, you'll see a big drop moving from one to two nodes. With enough parallelism, you will see close to double the throughput. Still, we usually look at scalability starting at 2-3 nodes, because a distributed system with one node is a different animal. This is something we address in our docs, but people naively testing VoltDB run into it more than we'd like. So for the next major release, we've re-worked how we do global ordering and can now achieve sub-millisecond latency on larger clusters in internal testing. Note that there's no change to our serializable consistency to achieve lower latency. So this new scheme has a huge impact on synchronous workloads, but the scalability with enough parallelism has been close to linear all along.