Disclosed herein in a preferred embodiment is an automated financial instrument brokerage system wherein a front end layer interacts with customers to generate activity requests for an intermediate layer. The intermediate layer preferably processes the activity requests and places financial instrument orders on a financial market if appropriate. A backend layer preferably provides data to the intermediate layer for processing activity requests. Multiple heterogeneous front end customer applications may be supported by the same intermediate layer. Further, multiple backend layer applications may interact with the intermediate layer in a manner transparent to the front end layer. Further, scalability can be achieved be partitioning various tasks of the intermediate layer onto separate servers, and more preferably on separate redundant servers. Load balancers may then be used in the intermediate layer to provide distributed access to these servers. Also disclosed herein is a caching technique whereby turnaround time for processing activity requests can be reduced by reducing the number of times that the intermediate layer needs to interact with the backend layer.