Building a Dynamic UI System at Carousell (Part 2)
Article Summary
Siaw Young from Carousell reveals how they built a server-driven UI system that lets them ship features without app releases. Think HTML for mobile apps—but way more powerful.
Carousell's engineering team developed a dynamic UI system called Fieldsets to solve a critical problem: how to support hundreds of product categories with unique attributes without hardcoding each one. This deep dive explains the architecture of their JSON-based schema that powers everything from sell forms to listing details.
Key Takeaways
- Fieldsets use a 4-level hierarchy: fields, groups, screens, and fieldsets stored as JSON
- Component reuse increases velocity: new features built faster as component library grows
- Server controls 'what to show', Fieldset service controls 'how to show it'
- System enables A/B testing and backward compatibility through variant and build parameters
- Same components power multiple journeys: sell forms, search filters, and listing pages
Critical Insight
Carousell's Fieldset system decouples UI from business logic, enabling server-driven updates that eliminate the need for app releases while creating multiplicative development velocity through component reuse.
