TypeScript with Node.js
Building a REST API with TypeScript
Architect a scalable, layered REST API with Express, Controllers, Services, and Zod validation.
Last Updated: July 29, 2026
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10 min read
Building production REST APIs requires structured layering: Controllers handle HTTP requests, Services manage business logic, and DTOs/Schemas handle validation.
1. Introduction & Architecture
2. Deep Dive & Core Concepts
Separating controllers from services ensures business logic remains testable independently of Express HTTP req and res objects.
3. Basic Code Example
4. Advanced Production Patterns
5. Interactive Code Playground
console.log("Layered REST API architecture ready.");6. Common Pitfalls & Edge Cases
Note: Wrap async express route handlers with an
asyncHandler or use Express 5 to ensure unhandled promise rejections reach global error middleware automatically.7. Interview Q&A & Quizzes
Q: Why separate Controllers and Services in REST API design?
A: Controllers deal with HTTP concerns (status codes, headers, req/res parsing), while Services encapsulate framework-agnostic business logic.
8. Summary Comparison Table
| Architecture Layer | Responsibility | Example Tech |
|---|---|---|
| Router | Endpoint path mapping | Express Router |
| Controller | HTTP Request/Response handling | Express Controllers |
| Service | Core domain & business rules | Plain TS Classes |