How Senior Engineers Structure SaaS Codebases

Most people structure their applications by asking where files should go, but the better question is who should be allowed to know what. In this video, we’ll break down how a production SaaS codebase is organized around ownership, boundaries, and responsibility instead of random folders. We’ll look at the dependency rule, naming conventions, vendor boundaries, and an end-to-end billing checkout request flow. The goal is simple: make every future change have an obvious place to go. 📸 My SaaS Starter Kit: https://www.syntaxpath.com/saas-start... 🤩 Get 50% off SyntaxKit with code YOUTUBE - available for the first 5 people only. 🔒 My favorite Auth Solution: https://dub.sh/xeU8r3v 💻 Learn to Code faster with Scrimba and Save 20% - https://scrimba.com/the-ai-engineer-p... 🌍 My Website: https://www.syntaxpath.com/ 👋🏻 Discord:   / discord   ✅ Follow me on X: https://x.com/janmarshaldev 📧 Business ONLY: [email protected] Timestamps: 00:00 Intro 00:59 Why Big Projects Become Hard to Structure 03:29 Folder Structure vs Architecture 07:00 SyntaxKit Monorepo Overview 08:00 Security and Boundary Protection 10:00 Naming Conventions That Scale 14:00 Code Organized by Responsibility 15:30 The Dependency Rule 20:00 How Each Layer Owns Its Job 24:00 Enforcing Boundaries with ESLint 27:00 Billing Checkout Request Flow