Prophecy: Using History for High-Throughput Fault Tolerance
Byzantine Fault-Tolerant (BFT) replication has enjoyed a series of performance improvements, but remains costly due to its replicated work. The authors eliminate this cost for read-mostly workloads through Prophecy, a system that interposes itself between clients and any replicated service. At Prophecy's core is a trusted sketcher component, designed to extend the semi-trusted load balancer that mediates access to an Internet service. The sketcher performs fast, load-balanced reads when results are historically consistent, and slow, replicated reads otherwise. Despite its simplicity, Prophecy provides a new form of consistency called delay-once consistency.