Exploiting speculation in partially replicated transactional data stores

Online services are often deployed over geographically-scattered data centers (geo-replication), which allows services to be highly available and reduces access latency. On the down side, to provide ACID transactions, global certification (i.e., across data centers) is needed to detect conflicts between concurrent transactions executing at different data centers. The global certification phase reduces throughput because transactions need to hold pre-commit locks, and it increases client-perceived latency because global certification lies in the critical path of transaction execution.