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.