Architecture

Recommended layout

apps/
  mobile/        Expo app for iOS, Android, and web
  api/           Fastify backend
packages/
  contract/      ts-rest route definitions and shared request/response types
  db/            Drizzle schema, migrations, and database helpers
  ui/            Optional shared React Native components

Recommended stack

• Expo for the client app surface.
• Fastify for the backend API.
• ts-rest for contract-first type sharing.
• Postgres with Drizzle for persistence.
• Better Auth or Clerk for authentication.
• Expo Notifications for the initial push path.

Why this shape

• The client apps stay aligned because the backend owns state.
• The contract layer prevents hand-written request/response drift.
• The database package keeps schema and migrations close together.
• Notifications can evolve later without reorganizing the project.