SQL Inbound Service write to internal Cache Table

I have the need to query an external database and write the result set/snapshot to an internal %Persistent [ DdlAllowed ] table that I built. I have built inbound SQL Services before and write them externally to replace SSIS jobs, but how would querying a database via a Service and writing the data to an internal table work?

Can I just take the inbound query structure and write it to the class file of the internal table in a DTL? If so, what would be the Target? Or does this need to be done within a BPL as a Code block?