Every modern digital product is, at its core, a collection of APIs. Whether you're building a web application, a mobile app, a SaaS platform, or an e-commerce store, the way you design and structure your APIs determines how quickly you can iterate, how easily you can integrate with other systems, and how gracefully your product scales.
API first development is an approach where the API is designed and built before the user interface. Instead of building a frontend and tacking on an API later, you define your API contracts upfront and build your entire product around them. This seemingly simple shift in order has profound implications for product quality, team velocity, and long term maintainability.
Why API First?
Decoupled Architecture
When your API is the source of truth for your business logic, your frontend becomes a consumer, just like any other client. This decoupling means you can rebuild your entire frontend without touching your backend. You can support web, mobile, and third party integrations from the same API. Different teams can work on frontend and backend simultaneously. You can switch technologies on either side without affecting the other.
Better Developer Experience
A well designed API with clear documentation becomes the contract that frontend and backend teams develop against. Frontend developers don't need to wait for backend endpoints to be ready. They can build against the API specification using mock servers. Backend developers can focus on business logic without being coupled to UI decisions.
Future Proofing
Building API first means your business logic exists independently of any particular interface. When you need a mobile app, the API is already there. When a partner wants to integrate with your system, the API is ready. When you decide to rebuild your frontend with a newer framework, the API remains stable.
Designing Great APIs
API design is both an art and a discipline. A well designed API is intuitive, consistent, and hard to misuse. Here are the principles we follow at Encode Digital.
- 1.Resource oriented design: Model your API around business resources (users, orders, products), not actions or UI components
- 2.Consistent naming: Use predictable, descriptive naming conventions across all endpoints
- 3.Proper HTTP semantics: Use the right methods (GET, POST, PUT, DELETE) and status codes (200, 201, 404, 422)
- 4.Versioning from day one: Plan for API evolution with a clear versioning strategy
- 5.Comprehensive error handling: Return structured, actionable error messages that help consumers fix issues
- 6.Pagination and filtering: Build these in from the start. Retrofitting them is painful
REST vs GraphQL: Choosing the Right Approach
The REST vs GraphQL debate isn't about which is universally better. It's about which fits your specific needs. REST is simpler to implement, widely understood, and benefits from excellent HTTP caching. GraphQL excels when you have complex data relationships, multiple client types with different data needs, or when you need to minimise network requests.
For most projects, a well designed REST API is the pragmatic choice. Consider GraphQL when you have multiple frontends with significantly different data requirements, or when over fetching and under fetching become measurable problems.
Authentication and Security
API security is non negotiable. Every API should implement proper authentication (JWT or OAuth 2.0 depending on use case), rate limiting to prevent abuse, input validation on every endpoint, CORS configuration that follows the principle of least privilege, and encrypted communication via HTTPS.
- Never expose internal IDs or system details in error messages
- Implement request signing for webhook endpoints
- Use API keys for service to service communication
- Log all API access for audit trails
- Set appropriate token expiry and refresh mechanisms
Documentation as a First Class Citizen
An API without documentation is an API that no one can use effectively. API first development naturally produces better documentation because the API specification is written before implementation. Tools like OpenAPI (Swagger) allow you to define your API contract, auto generate interactive documentation, create mock servers for parallel development, and generate client SDKs automatically.
Implementing API First in Your Organisation
Transitioning to API first development requires a shift in mindset more than a shift in technology. Start by designing your next feature API first. Write the specification before the implementation. Invest in API documentation tooling. Set up a mock server so frontend and backend can develop in parallel. Measure API quality metrics like response times, error rates, and consumer satisfaction.
At Encode Digital, API first is central to how we build. Every project starts with API design, ensuring our clients get products that are modular, integrable, and built to evolve. Whether you're building a new product or modernising an existing system, an API first approach sets you up for long term success.
Cover photo by Markus Spiske on Unsplash
