Final answer:
The tester's early identification of a potential design issue is best categorized as reducing the risk of fundamental design defects, which helps optimize the design for performance from the start.
Step-by-step explanation:
The tester's identification of a potential performance problem in a proposed database structure is an example of the testing contribution to success best described as reducing the risk of fundamental design defects. Early involvement of testers can lead to early discovery of design issues, which may result in significant improvements in the design before implementation. Such early feedback can help to prevent costly rework and ensure that the design is optimized for performance from the beginning, aligning with design principles and user requirements.