A system with multiple data stores receives a data access request that includes one or more variables. The system determines which data store can service the data access request by using mappings of the variables to the data stores in order to evaluate whether partition expressions for the data stores overlap with the variables in the data access request. The data access request is then sent to the data stores corresponding to the partition expressions that overlap. The partition expressions can have one or more variables. The present invention supports multi-dimensional partitioning.