APIs (Application Programming Interfaces) are the backbone of modern software. They enable systems to communicate, share data, and orchestrate complex workflows across platforms. Whether you're building a SaaS product, integrating third-party services, or connecting internal systems, API design decisions shape the reliability and scalability of your entire architecture.
REST vs GraphQL
REST
The most common API paradigm. Resources are represented as URLs, and standard HTTP methods (GET, POST, PUT, DELETE) define operations.
Strengths:
- Simple, well-understood, and widely supported
- Excellent caching with HTTP semantics
- Easy to debug with standard HTTP tools
When to use: Most CRUD applications, public APIs, microservices communication.
GraphQL
A query language that lets clients request exactly the data they need in a single request.
Strengths:
- No over-fetching or under-fetching
- Strongly typed schema serves as documentation
- Single endpoint reduces network overhead
When to use: Complex UIs with varied data requirements, mobile apps with bandwidth constraints, aggregating multiple data sources.
API Design Best Practices
Use Consistent Naming Conventions
- Resources are nouns: `/users`, `/orders`, `/products`
- Use plural nouns for collections
- Nest related resources: `/users/123/orders`
- Use kebab-case for multi-word resources: `/order-items`
Proper HTTP Status Codes
- `200` — Success
- `201` — Created
- `400` — Bad Request (client error)
- `401` — Unauthorized
- `403` — Forbidden
- `404` — Not Found
- `429` — Too Many Requests
- `500` — Internal Server Error
Pagination
Never return unbounded lists. Use cursor-based or offset-based pagination:
```
GET /users?cursor=abc123&limit=20
```
Versioning
Version your API from day one. Use URL versioning (`/v1/users`) or header versioning (`Accept: application/vnd.api+json;version=1`).
Authentication and Authorization
API Keys
Simple but limited. Best for server-to-server communication where the client is trusted.
OAuth 2.0 / JWT
The standard for user-facing applications. Issue short-lived access tokens and long-lived refresh tokens. Validate tokens server-side on every request.
Webhook Security
Sign webhook payloads with HMAC-SHA256 so recipients can verify authenticity. Include timestamps to prevent replay attacks.
Rate Limiting
Protect your API from abuse and ensure fair usage:
- Token bucket: Allow bursts while maintaining an average rate
- Sliding window: Count requests in a rolling time window
- Return headers: Include `X-RateLimit-Limit`, `X-RateLimit-Remaining`, and `Retry-After`
Error Handling
Return structured, consistent error responses:
```json
{
"error": {
"code": "VALIDATION_ERROR",
"message": "Email address is required",
"details": [
{ "field": "email", "rule": "required" }
]
}
}
```
Integration Patterns
Synchronous (Request/Response)
Direct HTTP calls. Simple but creates tight coupling. Use circuit breakers to handle downstream failures gracefully.
Asynchronous (Event-Driven)
Publish events to a message queue (e.g., AWS SQS, RabbitMQ). Consumers process events independently. Better resilience and scalability.
Webhooks
Push notifications from one system to another. The sender makes an HTTP POST to the receiver's URL when events occur.
How RCB Software Approaches API Development
We design APIs with long-term maintainability in mind — clear contracts, comprehensive validation with Zod, automated OpenAPI documentation, and thorough integration test suites. Whether you need a customer-facing REST API, a GraphQL gateway, or complex third-party integrations, we build APIs that are reliable, secure, and well-documented.