Decision tables are the most popular decision modeling constructs but they have a tendency to grow with time or to use huge arrays of data from the very beginning. When decision tables have tens and even hundreds of thousands of rules, their performance may go down. It becomes especially unacceptable when such big decision tables need to be executed a million times a day. This article describes how OpenRules deals with big decision tables executing even very large tables within milliseconds and giving its users a choice of where to keep and maintain their data: in Excel, in a CSV file, in a fixed-width file, or in a database. Link