Most current UI libraries provide great user experience with a vast of components. But when it comes to heavy customization and non-standard scenarios, especially for E-Commerce, they become hard to manage, scale or even slow down performance. How to create a UI library that provides users the most possible freedom in customizing components, while keeping our performance and scalability to the fullest? How much customization freedom is enough? What other lessons learned, during StorefrontUI, that can help other Vue developers in building their own system? That's what my talk's about.