A method of providing support at a server for GUI development is disclosed. At least a portion of a query is received from the client system. It is determined that a first field of a plurality of fields corresponding to a specified custom object type is to be resolved using a data item stored in a first server-side data store of the plurality of server-side data stores. It is determined that a second field of the plurality of fields corresponding to the specified custom object type is to be resolved using a data item stored in a second server-side data store of the plurality of server-side data stores. The data item stored in the first server-side data store is aggregated with the data item stored in the second server-side data store into a response to at least a portion of a query for sending to a client system.