  Byzantine-Fault-Tolerant (BFT) systems are rapidly emerging as a viable
technology for production-grade systems, notably in closed consortia
deployments for nancial and supply-chain applications. Unfortunately, most
algorithms proposed so far to coordinate these systems suffer from substantial
scalability issues, and lack important features to implement Internet-scale
governance mechanisms. In this paper, we observe that many application
workloads offer little concurrency, and propose PnyxDB, an
eventually-consistent Byzantine Fault Tolerant replicated datastore that
exhibits both high scalability and low latency. Our approach is based on
conditional endorsements, that allow nodes to specify the set of transactions
that must not be committed for the endorsement to be valid. In addition to its
high scalability, PnyxDB supports application-level voting, i.e. individual
nodes are able to endorse or reject a transaction according to
application-defined policies without compromising consistency. We provide a
comparison against BFTSMaRt and Tendermint, two competitors with different
design aims, and show that our implementation speeds up commit latencies by a
factor of 11, remaining below 5 seconds in a worldwide geodistributed
deployment of 180 nodes.

Databases;Distributed, Parallel, and Cluster Computing