Let me check if I understand your question correctly, you want to store your static access credentials in the database? The module currently does not support this, you would have to build that yourself. The module should only be used for generating the credentials object and the sigV4Headers object. These objects should not be stored in the database as they may only be valid for a limited period of time.
Perhaps this is something that will answer your question if you plan on using one of our connectors: https://docs.mendix.com/appstore/connectors/aws/amazon-polly/#authentication
Does this answer your question?