A CSS architecture developer designs and implements scalable and maintainable CSS code structures for web applications. They create style guides and design systems to ensure consistency across the application, and often use CSS pre-processors like SASS or LESS for efficient styling. They also manage the organization of CSS files and naming conventions, often using methodologies like BEM or SMACSS. Moreover, they handle CSS performance optimization and ensure the styles are responsive and cross-browser compatible. They work closely with front-end developers and designers, ensuring the visual interpretation of the design is accurately implemented.