Low-latency geo-replicated state machines with guaranteed writes

When deployed in geo-distributed environments, existing state-machine replication protocols require at least one widearea communication step for establishing a total order on client requests. For use cases in which clients are not interested in the actual result of a request, but just need a guarantee that the request will be processed eventually, this property usually incurs unnecessarily high response times. To address this problem we present Weave, a cloud-based georeplication protocol that relies on replica groups in multiple geographic regions to efficiently assign stable sequence numbers to incoming requests. This approach enables Weave to offer guaranteed writes which in the absence of faults only wait for communication within a client's local replica group to produce an execution guarantee for a particular sequence number. Our experiments with a distributed queue and a replicated log show that guaranteed writes can significantly improve response times of geo-replicated applications.