For decades, software teams responsible for building and managing core business applications have loyally adhered to code-first development practices. This means that once a business lays out its software requirements, developers will immediately start to code the applications, adjusting that code along the way in response to issues or updated requirements. While this was a perfectly fine approach within the confines of monolithic systems based mostly on a single language or framework, this is becoming a less effective practice as architectures become increasingly populated by diverse sets of languages, protocols, communication mechanisms and API integrations.
Development strategies that rely on code-first design techniques are becoming less efficient as both the development landscape and sophistication of APIs evolve. Software trends like microservices, serverless deployment and edge computing have increased the need for strategies that quicken the pace of development, one of these being the API-first approach. The high levels of autonomy promoted by API-first development make it a logical objective as an organization departs from monolithic application architectures in favor of more dynamic design and development paradigms.
In this article, we'll look at the basic ideas that underpin API-first development, examine the benefits and challenges of this approach, and explore some tools designed to help organizations safely adopt an API-first approach to software design.
What is API-first?
An API-first approach dictates that programmers determine exactly how the API will behave and address specific business requirements before any actual coding starts. API-first design also encourages developers to embrace a controlled fail fast methodology for updates, code changes and feature additions. Teams can build a single application as a catalog of small units of functionality with self-contained processes and their own lightweight communication mechanisms.
To start, development teams must document the specific functions and data needed to achieve a certain business task, solve a specific issue or add a particular capability to existing software. This will serve as a list of the key functions and services the APIs will need to expose. From there, developers can start to diagram the automated workflow and review cycles that will need to be in place. Once satisfied with the structure and design of the APIs and their planned lifecycle, teams can begin to write the blocks of code that will make up these APIs and, ultimately, the application.
Development team leads must make sure to create well-defined API contracts that enforce coding procedures and provide benchmarks for things like performance, error rates and availability. Both descriptive documentation and clear communications are high priorities here, particularly when working within distributed development teams spread across different time zones. This documentation should include things like requirement checklists, screenshots and links to related system designs.
Pros and cons of an API-first approach
Adopting an API-first approach allows organizations to rapidly build reusable application features, and then quickly deploy those features across multiple devices and channels. It can also simplify the process of adapting applications to satisfy new end-user demands and changing compliance requirements, thanks to accelerated prototyping and testing. Companies like Netflix, Amazon, Etsy and Uber have achieved unprecedented scalability through a combination of API-first design and microservice strategies.
However, API-first development requires considerable upfront planning, especially in large-scale enterprise settings where both business and development teams must learn new design methodologies, development workflows and strategies. An API-first transition doesn't just happen on its own, and requires dedicated IT leaders and C-suite buy-in.
Careful integration and testing is a mandatory part of API-first adoption. If programmers fail to maintain parity between multiple components in the development pipeline, systems will be plagued by chronically mismatched code, mock servers, test automation processes and documentation. API-first represents a serious development undertaking, particularly when live implementation failures become the only way to identify certain errors and their potential causes.
API-first development tooling
Alongside a well-defined API contract, an API style guide can also help structure key aspects of error handling, enforcing code formats, versioning strategies and other standard maintenance processes. To help with this, many API management providers offer tooling specifically calibrated to support an API-first design approach.
The following represents a selection of well-designed, comprehensive API management tools, some of which are readily available as open source projects:
SwaggerHub is an API development and documentation management platform that offers a versatile set of tools to support an API-first approach. This includes Swagger Editor and SwaggerUI, which are both included as part of the platform's API deployment faculties. SwaggerHub can act as a single source of truth for testing and deployment standards for API-first projects, and simplifies the process for developers to publish necessary style guides and documentation across an organization.
FastAPI is an open source web framework that caters to API-first projects and operates in a way that should feel familiar to developers who work with Node.js and Go. One of FastAPI's perks is that it's primarily based in Python, and provides developers access to the language's API-specific support features and libraries. This includes the asyncio library, which houses a variety of both high- and low-level APIs calibrated to support concurrent application processes.
Mulesoft's API Manager is a tool for modeling and describing API-first design specifications, and offers significant support for those using OAS or RAML. API Manager helps generate documentation, create mock APIs and perform service integration tasks. API Connect enables developers to create reusable API components known as RAML fragments and becomes a particularly powerful tool when used in conjunction with Anypoint Studio, Mulesoft's Eclipse-based integration environment.
Postman is a platform for API builds and deployments, and places a strong focus on documentation, monitoring, automated testing and creating mock APIs. Developers can quickly add API test suites that check for issues surrounding integration, performance and compliance with API contracts. Postman features a built-in editor that helps developers define APIs using standard specifications like Open API, RAML and GraphQL, and even allows teams to import their own specifications into an existing project.
Smartbear's ReadyAPI platform offers a suite of useful API-first design tools, many which revolve around creating CI/CD integrations with JIRA, Git, Slack and Jenkins. Companion tools such as SoapUI, LoadUI and ServiceV provide further testing and simulation capabilities for both RESTful and SOAP-based APIs, enhancing ReadyAPI's appeal as a centralized hub for an organization's API design projects. It's a particularly good option for organizations faced with strict security and performance requirements.