Inventory Extraction

I have a generic extractor as part of the Inventory Extraction Data Model. I need to enhance the extract structure with the Special Stock (SOBKZ) indicator. I am looking to use the MSEG table as my source table with the lookup keys as Plant, Material.

My concerns are whether the there will be a performance issue for the extractor if we are doing a lookup to MSEG. Is there a more suitable source table or will performance not be such an issue? Thanks