Design-First vs Develop-First: Navigating the Choices in REST API Development

Building a REST API involves a crucial choice between the Design-First and Develop-First approaches. Both have unique merits and challenges, and your project's needs will dictate the best fit. This article explores these paradigms and highlights how OpenAPI/Swagger can benefit either strategy.

Design-First Approach

Characteristics

Design-Centric: Starts with an API contract, detailing endpoints, responses, and data types.
Structured Workflow: Begins with design, followed by development and testing.

Advantages and Disadvantages

Pros: Facilitates team collaboration, enables automated testing, produces a stable API.
Cons: Requires upfront time, less flexibility to change.

Develop-First Approach

Characteristics

Code-Centric: Development starts with code, evolving the API iteratively.
Flexible Workflow: Testing and documentation happen alongside development.

Advantages and Disadvantages

Pros: Faster initial development, flexibility for change.
Cons: Potential inconsistencies, risk of inadequate documentation.

Comparison Chart

Category	Design-First	Develop-First
Initial Focus	API Contract	Code
Workflow	Structured	Flexible
Collaboration	Early, cross-team	Often developer-centric
Testing	Facilitated	On-the-fly
Documentation	Prioritized	Can be secondary
Flexibility for Changes	Limited	High

How OpenAPI/Swagger Adds Value

For Design-First

Standardized Contract: Enables creation of a detailed, standard API contract.
Code Generation: Automates code stub and SDK creation.
Automated Testing: Facilitates creation of mock servers and automated tests based on the API specification.

For Develop-First

Documentation from Code: Generates robust API documentation directly from code annotations.
Built-in Validation: Compares the developed API against the OpenAPI spec for compliance.
Interactive Testing: Provides an interactive user interface for easy endpoint testing.

Universal Benefits

Better Integration: Eases compatibility issues with third-party services.
Rich Ecosystem: Benefits from extensive community support and tooling.

Conclusion

Whether you choose Design-First or Develop-First, incorporating OpenAPI/Swagger can provide significant advantages, making your API more robust, easier to test, and simpler to maintain. Both approaches have their pros and cons, but with OpenAPI/Swagger, you’re better equipped to develop a high-quality API.