Byzantine fault-tolerant (BFT) replication has enjoyed a series of performance
improvements, but remains costly due to its replicated work. We 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 …

… D-Prophecy: A distributed sketcher … • Prophecy’s performance on reads approaches
that of unreplicated service • Relaxes consistency to delay-once semantics … • Prophecy’s
performance on reads approaches that of unreplicated service • Relaxes consistency to
delay-once semantics …