Fault tolerant operation is disclosed for a primary match server of a financial exchange using an active copy-cat instance, a.k.a. backup match server, that mirrors operations in the primary match server, but only after those operations have successfully completed in the primary match server. Fault tolerant logic monitors inputs and outputs of the primary match server and gates those inputs to the backup match server once a given input has been processed. The outputs of the backup match server are then compared with the outputs of the primary match server to ensure correct operation. The disclosed embodiments further relate to fault tolerant failover mechanism allowing the backup match server to take over for the primary match server in a fault situation wherein the primary and backup match servers are loosely coupled, i.e. they need not be aware that they are operating in a fault tolerant environment. As such, the primary match server need not be specifically designed or programmed to interact with the fault tolerant mechanisms. Instead, the primary match server need only be designed to adhere to specific basic operating guidelines and shut itself down when it cannot do so. By externally controlling the ability of the primary match server to successfully adhere to its operating guidelines, the fault tolerant mechanisms of the disclosed embodiments can recognize error conditions and easily failover from the primary match server to the backup match server.