How I Structured a Production-Ready Node.js Backend for SaaS

Most SaaS projects start the same way. You scaffold a Node.js backend, then gradually add authentication, billing, database models, email notifications, background jobs, and API documentation. After doing this repeatedly, I wanted a cleaner starting point for new projects. So I structured a backend foundation with the most common SaaS components already wired together. This is the architecture I ended up with. Tech Stack The backend is built with: Node.js TypeScript Express PostgreSQL Drizzle ORM Stripe (billing) Resend (transactional email) Zod (validation) OpenAPI / Swagger (API docs) The goal wasn't just to include these tools, but to organize them in a way that keeps business logic separate from infrastructure. Folder Structure This is the high-level folder structure used in the project: The backend is organized into layers so business logic, infrastructure integrations, and the HTTP layer remain isolated. API Documentation The API is documented using OpenAPI, making it easy to exp