A data processing method includes receiving a request to perform a calculation, identifying, based on the request, data items needed to perform the calculation and retrieving the data items from a data store, storing, in memory, the items, generating graphs for the calculation, wherein each graph comprises one or more nodes, each node comprising instructions to perform at least a portion of the calculation and at least one data item needed by the portion of the calculation, executing each of the graphs to generate a result for the calculation by traversing the graph and processing each node using the instructions of the node and the at least one data item of the node, wherein executing is performed without accessing the data store, and storing, in the data store, the result.