A Folder Structure That Scales for Full Stack SaaS

Short summary

A guide to organizing a full-stack SaaS monorepo using feature-based (vertical slice) folder structure instead of grouping by technical role. Covers NestJS module organization where each feature owns its controllers, services, DTOs, and tests, plus Next.js App Router route groups for frontend organization. The key principle: group by feature so adding a field touches one folder, not four.

• •Feature-based (vertical slice) folder structure prevents codebase rot as features grow
• •NestJS modules are natural feature boundaries — fighting them creates unnecessary friction
• •Keep a small common/ folder for cross-cutting concerns only; avoid premature sharing between features

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