HyperDex provides the strongest consistency properties of any open-source NoSQL system. Specifically, HyperDex guarantees that key operations are linearizable. All key operations are totally ordered and will be seen in the same order by all clients.
HyperDex ensures that every key-based operation is consistent every time. The consistency properties of the system are easy to understand and communicate without reference to the internal operation of the system. There is no need to understand complex consistency models, with poorly articulated edge-cases. Data consistency is guaranteed even through failovers.
A novel replication protocol called value-dependent chaining is responsible for these strong guarantees. While we defer to our relevant publications for an in-depth explanation of the implementation, the key idea is that nodes are arranged in a chain that passes through all replicas for an object. Consistency is guaranteed because the linear nature of the chain makes it easy to reason about the state of the system at all times.