Monorepo Setup Guide for Fullstack Applications

A monorepo is a single repository that contains multiple projects or packages. Instead of having separate repositories for your frontend, backend, and shared libraries, everything lives in one place. This makes it easier to share code, run cross-project tests, and ensure compatibility between your services. Companies like Google, Meta, and Microsoft use monorepos at massive scale. For startups, a monorepo simplifies the development workflow significantly.

Turborepo and Nx are the two leading monorepo tools for JavaScript and TypeScript projects. Turborepo, built by Vercel, focuses on build performance with intelligent caching and parallel execution. Nx, built by Nrwl, offers more features including code generation, dependency graphs, and enforced module boundaries. Turborepo is simpler to adopt incrementally, while Nx provides more structure for larger teams. Both tools dramatically improve build times by caching previous results.

Organize your monorepo into `apps` and `packages` directories. The `apps` folder contains your deployable applications like your Next.js frontend and Express backend. The `packages` folder contains shared libraries like your TypeScript types, UI components, and utility functions. Each package has its own `package.json` that declares its dependencies. Use workspace protocols to reference internal packages, so changes propagate automatically across your project.

One of the biggest advantages of a monorepo is sharing code between your frontend and backend. Create a shared types package that defines your API request and response types. Both your frontend and backend import from this package, ensuring they always agree on data shapes. Shared validation schemas using Zod work particularly well since they can validate data on both the client and server. Shared utility functions eliminate code duplication across projects.

Configure your monorepo tool to build packages in dependency order. When you run `turbo dev`, it starts all your applications and rebuilds packages when their source files change. Use environment-specific configurations for development and production builds. Set up shared ESLint and TypeScript configurations that all packages inherit, ensuring consistent code style and type checking across your entire codebase.

Monorepo CI/CD pipelines should only build and test packages that have changed. Both Turborepo and Nx support affected package detection, so you do not rebuild your entire codebase for every commit. Configure your CI provider to cache the monorepo tool's build cache for faster pipeline execution. Use separate deployment workflows for each application, triggered only when their dependencies change. This keeps deployment times fast even as your monorepo grows.

Migrating from multiple repositories to a monorepo requires careful planning around dependency management, build configuration, and CI/CD setup. AI-generated projects often start as standalone applications that become harder to maintain as features grow. SpringCode restructures AI-built codebases into well-organized monorepos with shared types, efficient build pipelines, and proper CI/CD configuration.