Api First Design

31 May 2023 · 10 min

In today’s interconnected software landscape, APIs (Application Programming Interfaces) serve as the critical building blocks for communication and data exchange between different components and systems. Not only within the systems operated by a single person or team, but often also across applications owned by different teams.

Without a clear and well-defined API contract, coordination between teams becomes cumbersome and error-prone, standing in the way of efficient integration. To address this challenge, organizations are increasingly adopting an API first design approach. In this blog post, we will explore the concept of API first design, its significance in achieving efficient and effective integration, and practical steps to implement it successfully.

🧐 Understanding the challenges of API design and coordination

API design and coordination present significant challenges that can impact the efficiency and effectiveness of development teams. These challenges involve both the coordination between API producers and consumers and the design considerations during the development process. Understanding and addressing these challenges is essential to ensure seamless integration and mitigate potential issues.

The challenge of API coordination

Effective API coordination involves collaboration between multiple teams, including API producers and consumers. When API coordination is lacking, API consumers may need to wait for the API producer to define and release the API, resulting in development delays and slower time to market. Establishing clear boundaries and expectations between teams is important to enable efficient collaboration and integration.

The impact of API design

While API coordination is crucial, the design of the API itself plays a vital role in the success of software integration. Poor API design or treating it as an afterthought in the development process can lead to issues such as exposing implementation details or business logic. This can cause breaking changes, versioning problems, and insufficient consideration of security aspects. Not having a proper API design can undermine the reusability, maintainability, and security of the integration, introducing complications that hinder long-term success. Because once a bad API is out there, it will be very hard to get rid of.

With a sufficient number of users of an API, it does not matter what you promise in the contract: All observable behaviors of your system will be depended on by somebody. Hyrum’s Law

To overcome these challenges and bringing your APIs to a higher quality standard, adopting an API first design approach is crucial. By making API design a fundamental consideration from the start, teams can achieve cohesive and maintainable software systems.

🙋 What is API first design

API first design is an approach that prioritizes the design and definition of the API contract as a fundamental step in the software development process. It involves treating the API as a product, with careful consideration given to its usability, reusability, and maintainability. By prioritizing the API contract from the beginning, teams can establish a clear interface and set of expectations for API consumers, promoting efficient collaboration and reducing integration challenges.

🌟 The impact of API first design

API first design brings numerous benefits to the software development process and the overall ecosystem. By embracing API first design, organizations can achieve:

• Loose coupling and high cohesion: Well-designed APIs with clear boundaries and responsibilities improve loose coupling and high cohesion between software components. This allows for the reuse of APIs across different projects and systems. Read more on tight coupling.

• Improved collaboration and communication: The deliberate focus on API design promotes better collaboration and communication between development teams, stakeholders, and domain experts. A shared understanding of the API contract and its purpose enhances coordination and reduces misunderstandings.

• Enhanced developer experience: API first design provides well-documented and consistent API contracts, making it easier for developers to understand, integrate, and build functionalities specific to their applications. This streamlined onboarding process reduces the learning curve, eliminates the need to reinvent the wheel, and allows developers to work more efficiently, speeding up development and reducing time-to-market.

• Better error handling and debugging: API first design promotes the consideration of error handling and debugging mechanisms. By incorporating robust error handling and informative error messages in the API contracts, developers can easily identify and troubleshoot issues, leading to more reliable and resilient software solutions.

• Enhanced security and stability: Considering security requirements during the design phase ensures that APIs are designed with security in mind. By enforcing access controls, data encryption, and other security measures, API first design establishes a robust foundation for secure integrations.

🚀 Implementing API first design

To successfully implement API first design, organizations should consider the following key aspects:

API guidelines and style guide

Establishing clear and comprehensive API guidelines, along with a style guide, promotes consistency and coherence in API design across the organization. These guidelines should cover aspects such as naming conventions, formatting, proper use of http response codes, error handling, versioning, and REST basics. API guidelines help ensure that APIs are self-explanatory, easy to use, and conform to industry best practices. The Zalando API Guidelines are a good starting point, although a much simpler version should also suffice. Creating an API guild or similar group can help facilitate the adoption and consistent use of the guidelines across teams.

Ubiquitous language

A critical aspect of API first design is establishing a ubiquitous language that bridges the communication gap between (and within) development teams, stakeholders, and domain experts. By using a common vocabulary and language aligned with the business domain, everyone involved can better understand and collaborate not only on API design decisions, but also on other aspects of application development. The most important thing is to find OK (not even great) names for things and make sure everyone sticks with them. If you want to learn more about this you can look into Domain-driven design. Naming things is not only important in external API’s, but also internal once. Read more about that in Naming things.

Leveraging REST architecture

REST (Representational State Transfer) architecture provides a well-defined set of principles and constraints for building scalable and interoperable APIs. By adhering to RESTful design principles, such as resource-oriented design and statelessness, teams can create APIs that are consistent, intuitive, and easy to consume. It is important to educate the development teams about RESTful principles and provide guidance on their implementation to ensure uniformity and adherence to best practices. Creating resources for processes (or state changes) and not just entities can be a great way to a truely RESTFul API.

Creating an API contract

An API contract, typically represented using the OpenAPI specification, serves as a blueprint for designing APIs. It is best to start by manually writing the API specification, allowing you to define the contract before writing any code. This approach enables clear communication with potential API consumers, gathering their feedback and ensuring alignment with their expectations. Iterate on the API contract based on feedback, ensuring that it accurately captures the intended behavior and interfaces of the API before ever writing the first line of code.

Manually writing the API contract offers several advantages. It allows for thorough consideration of design decisions, naming conventions, and resource definitions, involving not only developers but also the entire team and stakeholders.

Once an API is implemented, it can be beneficial to start generating the API specification from code to avoid deviations between the spec and the code. Alternatively, you can validate that the code actually implements the manually written API specification using libraries like swagger-request-validator from Atlassian.

Security by design

In API first design, security is not limited to determining who has access to the application but extends to defining access control to specific resources (who is allowed to see what?). With a multitude of resources and processes, it can become complex to manage and authorize access to various entities. Consider scenarios where other applications, customer care agents, developers, or sometimes other users need access to resources owned by users. To address this challenge, it is crucial to incorporate security considerations during the specification and design an authorization model that ensures appropriate access to resources. Starting with a clear understanding of the different roles and their corresponding access levels, organizations can implement robust security mechanisms and authentication protocols to safeguard sensitive data and maintain data integrity throughout the API ecosystem.

🌐 Companies embracing API first design

Numerous companies have recognized the importance of API first design and have successfully incorporated it into their development processes. One prominent example is Amazon, which played a pivotal role in popularizing the API first approach. Amazon introduced an API Mandate that revolutionized their internal development practices. The mandate required all teams within Amazon to embrace these fundamental principles:

• Expose their data and functionality through service interfaces.
• Teams must communicate with each other through these interfaces.
• Design all service interfaces, without exception, from the ground up to be externalizable.

By adhering to these principles (which can be considered a predecessor to API first approach), Amazon has built flexible, modular systems, enabling seamless integration between various teams and driving innovation within the organization.

Another notable company that has led by example in API first design is Zalando, known for their API guidelines which are used and adopted all over the industry. Zalando’s commitment to API first design has empowered them to create scalable and interoperable systems, facilitating collaboration with external partners and supporting their rapid growth.

Furthermore, Twilio has achieved remarkable success through its API first design approach. Twilio provides a simple yet powerful interface that allows developers to integrate phone capabilities into their applications with ease. By reducing the complexities of telephony to just five API calls, Twilio has simplified the development process and attracted a wide range of clients worldwide. Twilio’s API-first platform has become a go-to solution for businesses seeking reliable and scalable communication services.

We have taken the entire messy and complex world of telephony and reduced it to five API calls. Twilio CEO, Jeff Lawson - During his seed pitch

These examples showcase the transformative impact of API first design on businesses, empowering them to deliver flexible software solutions while fostering collaboration and innovation. By following in the footsteps of industry leaders like Amazon, Zalando, and Twilio and embracing API first design principles, organizations can unlock the potential of seamless integration and stay ahead in today’s digital landscape.

These examples showcase the transformative impact of API first design on businesses, empowering them to deliver flexible software solutions while fostering collaboration and innovation. By following in the footsteps of industry leaders like Amazon, Zalando and Twilio and embracing API first design principles, organizations can unlock the potential of seamless integration and stay ahead in today’s digital landscape.

🚀 Embracing API first design for efficient and effective software integration

While API first design brings numerous benefits to the software development process, its successful implementation requires continuous iteration, collaboration, and adaptation to meet evolving needs and expectations. Organizations must overcome the challenges of API coordination, adopt a ubiquitous language, leverage REST architecture, create comprehensive API guidelines, and consider security by design. By prioritizing API design from the start and following best practices, organizations can establish a solid foundation for successful software integration.

Drawing from personal experiences, I have witnessed both the challenges and successes of API first design within different organizations. During my time at Rabobank, the API first transformation was initiated but did not take off effectively. API guidelines were created based on the Zalando guidelines, but teams often skipped reading them fully due to their length, resulting in poor adoption. API designs were not consistently created with externalization in mind, and industry best practices were often overlooked. However, a dedicated team (which we used to call the “API police”) was responsible for reviewing APIs exposed to the outside world. Although they had limited information to work with, they provided valuable insights into both good and bad design choices. I hope that since my departure, Rabobank has made progress in embracing API first design and achieving higher quality APIs.

In contrast, within Twill, I spearheaded the API first design approach, introducing simplified API guidelines based on the principles of Zalando. We established an API guild to update and maintain the guidelines, manage adherence to them, and support each other in API design. Currently, we are focusing on implementing automated API linting and initiating a review process for new and existing APIs. These efforts aim to pave the way for a more cohesive and efficient development process, promoting collaboration and API design excellence.

In conclusion, embracing API first design is an ongoing journey that requires commitment, collaboration, and a willingness to adapt. By addressing API coordination challenges, establishing a common language, leveraging REST architecture, creating comprehensive API contracts, and prioritizing security, organizations can achieve efficient and effective software integration. Through API first design, businesses can unlock the potential of enhanced collaboration, streamlined development cycles, and the delivery of high-quality software solutions, giving them a competitive edge in today’s digital landscape.