A system, apparatus, and method for providing real-time or pseudo real-time processing of transactions for a set of clients using a common or partially common rule base. Each client is assigned to a tier or category with the tier or category defined by specified performance criteria. In some embodiments, the specified performance criteria includes a false positive ratio (FPR). A rule for processing transactions is defined as a combination of an interval of a scoring range of a first risk assessment scoring system and an interval of a scoring range of a second risk assessment scoring system. A proposed rule is tested by determining if its performance falls within a defined range of the performance criteria when applied to data for previous transactions. If application of the rule satisfies the performance criteria, then the rule is accepted as part of the rule base for that tier or category of clients.