wursor/docs/decisions/0011-fastify-react-stack.md

11. Fastify is the API server; React + Vite is the web shell

• Status: Accepted
• Date: 2026-08-15

Context

IMPLEMENTATION §1 names "Express/Fastify" for the backend and "React + TypeScript" for the frontend. Sprint 1 required committing to one server framework before the first route and test.

Decision

Use Fastify for api/, and React 19 + Vite + vitest + @testing-library/react for web/.

Options considered

• Express (matches the plan's pseudocode).
• Fastify (chosen).

Rejected

• Express — the plan allows either; Fastify ships built-in JSON-schema validation, native async handlers, and first-class TypeScript, which removes glue the plan would otherwise write by hand.

Consequences

• Route handlers return via Fastify's reply object and validate payloads schema-first (the signup route enforces email format and password length).
• Future routes should keep using Fastify schema validation at the boundary rather than hand-rolled checks.