SDUI at Scale: GraphQL & Elixir at Cars.com with Zack Kayser

Elixir Wizards

Zack Kayser, Staff Software Engineer at cars.com, joins Elixir Wizards Sundi Myint and Charles Suggs to discuss how Cars.com adopted a server-driven UI (SDUI) architecture powered by Elixir and GraphQL to deliver consistent, updatable interfaces across web, iOS, and Android.

We explore why SDUI matters for feature velocity, how a mature design system and schema planning make it feasible, and what it takes, culturally and technically, to move UI logic from client code into a unified backend.

Key topics discussed in this episode:

• SDUI fundamentals and how it differs from traditional server-side rendering
• GraphQL as the single source of truth for UI components and layouts
• Defining abstract UI components on the server to eliminate duplicate logic
• Leveraging a robust design system as the foundation for SDUI success
• API-first development and cross-team coordination for schema changes
• Mock data strategies for early UI feedback without breaking clients
• Handling breaking changes and hot-fix deployments via server-side updates
• Enabling flexible layouts and A/B testing through server-controlled ordering
• Balancing server-driven vs. client-managed UI
• Iterative SDUI rollout versus “big-bang” migrations in large codebases
• Using type specs and Dialyxir for clear cross-team communication
• Integration testing at the GraphQL layer to catch UI regressions early
• Quality engineering’s role in validating server-driven interfaces
• Production rollback strategies across web and native platforms
• Considerations for greenfield projects adopting SDUI from day one
• Zack and Ethan's upcoming Instrumenting Elixir Apps book

Links mentioned:

https://cars.com
https://github.com/absinthe-graphql/absinthe
Telemetry & Observability for Elixir Apps Ep: https://youtu.be/1V2xEPqqCso
https://www.phoenixframework.org/blog/phoenix-liveview-1.0-released
https://hexdocs.pm/phoenix_live_view/assigns-eex.html
https://graphql.org/
https://tailwindcss.com/
https://github.com/jeremyjh/dialyxir
https://github.com/rrrene/credo
GraphQL Schema https://graphql.org/learn/schema/
SwiftUI https://developer.apple.com/documentation/swiftui/
Kotlin https://kotlinlang.org/
https://medium.com/airbnb-engineering/a-deep-dive-into-airbnbs-server-driven-ui-system-842244c5f5
Zack’s Twitter: https://x.com/kayserzl/
Zack’s LinkedIn: https://www.linkedin.com/in/zack-kayser-93b96b88

Special Guest: Zack Kayser.