Yelp Engineering and Product

Shawn Walton, Software Engineer

August 4, 2026

In early 2017, Webcore selected Flow as Yelp’s next-generation typechecker over TypeScript. At the time there was no clear frontrunner. Flow had better support for React, better performance, and a respectable repository of types for NPM packages in flow-typed. However, a few years later the landscape had shifted, and it became clear that TypeScript was emerging as the stronger choice. TypeScript’s DefinitelyTyped repo had thousands more packages than flow-typed, and many more packages shipped with built-in TypeScript headers. TypeScript also proved to be more stable over time, and limited uptake in the wider JS community made finding tools and documentation...

Igor Kusakov, Software Engineer

July 16, 2026

Introduction At Yelp, we rely heavily on GraphQL and Apollo for data loading in our frontend React monorepo. When a developer writes a GraphQL query or mutation inside a React component, the shape of the response is defined by the query itself — but TypeScript has no way to know what that shape looks like at compile time. That’s where code generation (codegen) comes in. We rely on codegen to read our queries and server schema, then produce TypeScript type definitions for every operation’s input variables and output data. In our codebase, this looks like: src/components/UserProfile/ ├── UserProfile.tsx ← contains...