51 min read

What is API-First Development & Why Is It Worth The Hype?

API-first is an approach where the API is "designed" before the UI. There are particular use cases where this approach is king.

Tim Davidson
Tim Davidson

API-first is a modern software development approach where an Application Programming Interface (API), is designed before the user interface and other parts of an application. This means the API is treated as a discrete product rather than an afterthought integration.

The API-first approach enables developers to focus on the core functionality and data of the application, as well as the structure and logic of the API, before designing and developing the UI and visual features. This approach also encourages modularity, scalability, and reusability of an application’s components since products are designed around an API from the ground up.

API-first is commonly used for building web applications and services under the principles of a microservices architecture. With this approach, developers can create flexible and decoupled applications well-suited to handling complex and evolving business requirements.

For many entrepreneurs and business owners, the concept of designing an API first is tricky to understand and implement. You’re leaving the comfort of looking at a Figma design and suggesting visual changes and moving into data relationships and conceptual functionality. It’s not something to shy away from but it requires a shift in how you prepare requirements and coordinate with your dev team.

In this article, we will explore the concept of API-first development, its benefits, best practices, and common challenges.

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    Core principles of API-first development

    API comes first, then implementation

    In API-First Development, the API is designed and developed before any other application components. This approach allows developers to define the core functionality and data of the application in the API, making it easier to create user interfaces and other components that work seamlessly with the API.

    By focusing on the API first, the dev team can create more modular and reusable software architectures that can be easily integrated with other applications and services.

    API-first prioritizes testing early and often

    By prioritizing testing early and often, developers can ensure that the API is functioning as expected and meets the needs of the business and the end-users.

    Under an API-first approach, testing should be integrated into the development process, with automated testing tools used to test the API regularly.

    A good supporting methodology is Test-Driven Development. We've written on this topic in a separate article, so we won't rehash too much content, but the idea is that tests come first, followed by development. This approach plays nicely with API-first because the test is written for what the API should do, the API is developed, and when it passes, the next feature moves into focus.

    API design should be based on business requirements

    When designing APIs, it is important to start with a clear understanding of the business requirements of the application. The API should be designed to meet the needs of the business, such as supporting specific use cases, data flows, and integrations. By aligning the API design with the business requirements, developers can create a system that is both functional and effective.

    In our experience, gathering requirements that are defined well enough to execute API first development is rare. In order to build the API, the dev team need to know the objects, their properties and their relationships.

    We're big advocates for Product Roadmapping, which can help your team get 95% of the way to having this information, but there still needs to be a point where you sit down and build a good old-fashion Univeral Modelling Language diagram (pictured below) that thoroughly lists the details that will inform API development.

    UML diagram example required for API-first development

    APIs should be designed to be modular, scalable, and reusable

    API-First Development emphasizes the importance of creating APIs that are modular, scalable, and reusable. Modularity allows APIs to be broken down into smaller, more manageable components that can be reused across multiple applications and services. Scalability ensures that APIs can handle increasing data and traffic as the application grows. Reusability makes it easier to maintain and update the system over time.

    APIs should be well-documented and easy to use

    Well-documented APIs are essential to ensuring that developers can quickly and easily integrate with the API. Documentation should be clear and concise, with examples and use cases demonstrating how the API works. Additionally, the API should be easy to use, with a consistent interface and error handling that provides developers with the information they need to debug issues.

    API-first documentation

    The image above is a great example of the documentation we're maintaining for a rather complex MACH (Microservices, API-first, Cloud-native, and Headless) project. Each endpoint has its own set of documented specifications, and the docs allow the methods to be tested.

    Prioritizes security and performance

    Security and performance are critical considerations when designing APIs. Security measures should be implemented to protect sensitive data and prevent unauthorized access. Performance should be optimized to ensure that the API can handle high traffic volumes and respond quickly to requests.

    Iteration and collaboration

    API-First development is a collaborative process that involves input from multiple stakeholders, including developers, business analysts, product owners, and users. Feedback from these stakeholders should be incorporated into the API design to ensure that it meets the needs of the business and the end users. This iterative process helps to ensure that the API is designed correctly from the outset, reducing the need for expensive and time-consuming rework later on.

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      Benefits of API-first approach

      API-First design is a response to problems that arise following a traditional linear development approach. It's no golden bullet, but it does have some concrete benefits.

      Reducing the "gotchas"

      The challenge in designing API-first is there's a lot of careful thought required to create a list of all the endpoints and what they'll expose. It's less intuitive than visual planning. However, the benefit is that it quickly exposes potential problems across the system.

      Depending on what your system looks like, a lot of the time, the API planning will revolve around what the frontend needs from the backend to accomplish its goal. Planning to have a search feature? We'll need an endpoint for that. But what if we need to order the data? And what data should be available for searching?

      There are tons of questions that need to be answered along the way, but making sure everything fits together, and the backend functionality is correctly exposed catches a lot of those "gotchas" before they arrive.

      Improving velocity

      API-first design takes all guesswork out of building connections between the decoupled components. It's a detailed plan for the flow of information between systems that requires a list of data required from each endpoint.

      Creating a detailed plan like this takes a decent amount of effort and forward-thinking. But it's quicker to think deeply about what needs to happen for an hour than it is to try and build a new feature for four hours, only to find the frontend is blocked by something missing in an API endpoint.

      Mentally mapping the dependencies and API requirements out helps improve velocity by removing those annoying blockers.

      Adds structure to complexity

      Software developers constantly wrestle with complexity and how to handle conceptually difficult problems. For repeatable problems, the typical approach is to figure out a good way to bring organization to the chaos and then refine that method into a framework.

      API-first design is exactly this. It's a framework for adding structure to complex architectures. Some features requiring data from several different APIs can practically too difficult to figure out without spending some time planning how everything connects together.  

      Promotes collaboration

      API-First development promotes collaboration by involving all key players in the development process early on. Developers get to work closely with other teams, such as product managers and user experience (UX) designers, to design the API that will be used to build the product or service. This approach helps to align the development process with the overall goals of the business, and ensure that the end result meets the needs of the end-users.

      The approach further promotes collaboration among developers since it involves establishing clear API documentation and design principles. This way, the development team works under a shared language and framework; thereby ensuring that they work towards a common goal and easily communicate with each other about how the API will be used.

      Improves developer experience

      In API-first development, APIs serve as the building blocks of an application. As such, the APIs often come with comprehensive documentation and easy-to-use tooling. This makes it easier for developers to get started and build on top of the API, reducing the learning curve and improving productivity.

      Also, by designing the API first, developers can create modular and reusable components that can be shared across different parts of the system. This not only helps to reduce redundant code but also allows developers to test and debug the API separately from other components, consequently saving time and improving the overall development experience.

      Enhances scalability

      APIs designed with an API-First approach are often more scalable than other APIs, as they can be easily extended or modified to accommodate growth and changes in the system. This allows businesses to build applications that can adapt to changing market conditions and user needs, without requiring costly and time-consuming rewrites.

      Drawbacks of API-first development

      Although API-first development can provide significant benefits, it also comes with some drawbacks.Here are some of the common challenges of adoption the API-first development:

      Design complexity

      One of the challenges of API-First Development is the complexity of designing an API that meets the needs of both the business and the end-users. API design requires a deep understanding of the business requirements, the system architecture, and the needs of the end-users. It can be difficult to strike the right balance between flexibility, functionality, and simplicity.

      Integration complexity

      Another challenge of API-First Development is integrating the API with existing systems or services. The API needs to be compatible with a wide range of systems, which can be challenging to achieve. Additionally, there may be security, compliance, or performance issues that need to be addressed during the integration process.

      Testing complexity

      Testing an API can be more complex than testing other components of the system. The API needs to be tested in isolation as well as in combination with other components. Additionally, testing the API requires a deep understanding of the API design and functionality, which can be time-consuming and require specialized skills.

      Governance and management

      API-First Development requires a strong governance and management framework to ensure that the APIs are designed and used in a consistent and secure manner. This can be challenging to achieve, especially in large organizations with many developers and teams.

      API-first best practices

      We use the concept of API-first daily as we build large headless eCommerce sites and decoupled applications. Here are our tips on best practice:

      1. Start with a clear API strategy

      Start by defining your API design guidelines like security, testing, and maintenance. Figure out your naming conventions for endpoints, parameters, and response codes. Keep them clear and consistent.

      2. Desing your API

      Before writing any code, design your API using a tool such as OpenAPI, RAML, or Swagger. This will help you to define the API's endpoints, data models, and operations and ensure that it is well-documented and easy to use.

      3. Use a consistent data model

      A consistent data model should be used across all APIs to ensure that they are interoperable and can be easily integrated with other systems. This can be achieved through the use of common data structures and data formats.

      4. Use HTTP verbs appropriately

      Use the appropriate HTTP verbs (GET, POST, PUT, DELETE) for each operation to ensure your API is RESTful and easy to use.

      5. Use versioning

      Use versioning to maintain backward compatibility and avoid breaking changes. Use URL or header-based versioning to allow clients to specify which version of the API they want to use.

      6. Document comprehensively

      Comprehensive documentation is critical to the success of an API-first development project. Documentation should include information on how to use the API, its features and limitations, data formats, use endpoints, handle errors and any authentication or authorization requirements.

      Documentation should be regularly updated and made available to developers through a developer portal or other centralized location. This helps to reduce confusion and ensure that developers have the information they need to integrate with the API effectively.

      Providing comprehensive documentation can also help to promote the adoption of the API by external developers and foster a sense of trust and credibility in the organization offering the API.

      7. Test your API

      Test your API thoroughly using automated testing tools to ensure that it is working correctly and handling errors appropriately.

      8. Implement authentication and authorization

      APIs are usually accessed by external and internal users, meaning that you have to maintain high-security standards to prevent unauthorized access to sensitive data. Enterprises, therefore, must implement strong authentication and authorization mechanisms to ensure that only authorized users and systems can access the API.

      One of the most common methods is to use API keys, which are unique identifiers that are provided to authorized users. API keys can authenticate requests and determine which actions a user is authorized to perform.

      Another method is to use OAuth, which is an open standard for authentication and authorization. OAuth is commonly used by web-based APIs and allows users to grant permission to third-party applications to access their data without revealing their passwords.

      9. Monitor API usage

      Monitoring API usage involves tracking and analyzing API usage data. This helps developers gain insights into how the API is being used, which features are popular, and which endpoints are being accessed the most. This information can be used to optimize the API's performance, identify potential issues or bottlenecks, and make informed decisions about future development efforts.

      It can also help reveal potential security threats, allowing developers to respond early enough to prevent losses.

      Frequently asked questions

      Q: What is API-First Development?

      A: API-First Development is an approach to software development that prioritizes the creation of a well-designed API before implementing the backend and frontend of an application. This approach allows for greater collaboration between development teams and can result in a more streamlined and efficient development process.

      Q: How does API-First fit into the MACH architecture?

      A: API-First is a key component of the MACH architecture, which emphasizes the use of modular, API-driven solutions for building digital experiences. An API-First approach can help organizations better integrate new technologies and respond quickly to changing market demands.

      Q: Can API-first development be used for all types of software projects?

      A: API-first development is generally best suited for complex software projects that involve multiple teams or systems. It is particularly useful for projects that require flexibility and scalability, as well as those that rely heavily on integration with external services or data sources. However, smaller or simpler projects may not benefit as much from an API-first approach, and it may be more efficient to develop the UI and API in tandem.

      Wrapping up

      In today's fast-paced technological landscape, API-first development has become a key factor in building robust and scalable applications. As more companies adopt this approach, developers need to stay up-to-date with the latest tools and techniques. By embracing API-first development, businesses can enhance their competitive advantage, innovate more quickly, and provide better user experiences. With the right planning, tools, and practices, API-first development can be a game-changer for any organization looking to build powerful and flexible software solutions.

      Written by
      Tim Davidson

      Tim Davidson

      Tim is the face of the company. When you want to kick off a new project, or an update on your existing project, Tim is your man!

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