1. A computer-implemented method comprising: a. In a target system, accessing a plurality of record identifiers received from an external source database; b. Storing the plurality of record identifiers in an electronic memory (“memory”) of the target system as elements of a software stack (“stack”); c. Reading a first plurality of the plurality of record identifiers (“first plurality”) from the stack and into a first thread, whereby the first plurality is thereupon excluded from the stack; and d. Applying the first thread to retrieve from the source database each record associated with each record identifier of the first plurality.