In this paper, we argue for the need and benefits for providing Byzantine fault tolerance as a service to mission critical Web applications. In this new approach to Byzantine fault tolerance, an application server can partition the incoming requests into different domains for concurrent processing, decide which set of messages that should be totally ordered, or not at all, based its application semantics. This flexibility would reduce the end-to-end latency experienced by the clients and significantly increase the system throughput. Perhaps most importantly, we propose a middleware framework that provides a uniform interface to the applications so that they are not strongly tied to any particular Byzantine fault tolerance algorithm implementation.