Building Scalable APIs: A Practical Guide
Most APIs start simple — a few endpoints, basic CRUD, maybe some authentication. But as your product grows, the cracks start to show. Here's how I approach API design from day one to avoid painful rewrites later.
Start with the Schema
Before writing any endpoint, I design the database schema. Tools like Drizzle ORM or Prisma let you define your schema in code and generate migrations automatically. A well-designed schema prevents 80% of API problems.
Use Layers
I structure every API with three layers:
- Routes — Define endpoints and validate input
- Services — Business logic, completely decoupled from HTTP
- Repositories — Database queries, easily swappable
This separation means I can test business logic without spinning up a server, and swap databases without touching service code.
Authentication & Authorization
JWT for stateless auth, refresh tokens for security. I use middleware to verify tokens and attach user context to every request. Role-based access control (RBAC) for authorization — keep it simple until you need something more complex.
Rate Limiting & Caching
Redis for both. Rate limiting protects your API from abuse. Caching reduces database load. Both are essential for any production API.
Error Handling
Consistent error responses with proper HTTP status codes. Every error includes a machine-readable code, a human-readable message, and optional details. Your frontend developers will thank you.
Monitoring
You can't fix what you can't see. Structured logging, health check endpoints, and request tracing are non-negotiable in production.