VoltDB achieves concurrency via scheduling, rather than shared access to data structures. There are concurrency primitives around networking/messaging and tran

VoltDB achieves concurrency via scheduling, rather than shared access to data structures. There are concurrency primitives around networking/messaging and transaction scheduling, so there aren't truly ZERO locks in the system as a whole. The big difference is that VoltDB has zero system-locks (mutexes,etc) around table data and indexes. It also has no logical locks/latches arounds indexes and rows like other systems. This makes executing SQL very fast. Because it doesn't wait on disk or on mutexes, SQL execution is typically bottlenecked on memory bandwidth.