The Primer Design System powers many of the experiences you see on GitHub today. From buttons to banners to breadcrumbs, these foundational components are required to be accessible, flexible, and performant across a wide variety of scenarios. Back in 2023, the number of components on certain pages began to explode. This led to several performance-related challenges with our existing CSS-in-JS solution: Initial page loads took longer due to styles being initialized on the client Server-side rende...