To optimize the performance when retrieving a large number of rows from a Data Extension via the API:

Use a SimpleFilterPart to retrieve small sets of relevant data (A) - This approach helps in fetching only the necessary data by applying filters, thus reducing the amount of data transferred and processed.

Use the ContinueRequest feature (C) - This feature in the SOAP API allows for pagination of results, making it possible to handle large sets of data in manageable chunks.