API-first development—why it is something to consider


The API-first approach for constructing apps and products is growing in popularity, with supporters citing business advantages and development agility as the main advantages. It’s worth our time, then, to detail exactly what API-first is, and why its use is becoming more widespread.


The “API” in API-first

The term API is fast becoming a commonplace piece of jargon from the API economy found often in business environments, and so too is the related term “API-first.”

However, many people who encounter these terms will still have a less than complete grasp of what they mean. If we are going to examine and state the benefits of the API-first approach, then we have to define exactly what an API is, and then we can explain the API-first strategy.

“API” stands for “application programming interface.” Simply put, it is a mediator that works to allow two distinct applications to talk to each other and so send data back and forth. This allows different apps to each offer’s functions to the user.

It can be helpful to view the API as an interpreter who is able to relay messages back and forth between two people who don’t have a language in common. The presence of the interpreter allows these two people to communicate with each other, where otherwise such communication would not be possible.

API endpoints determine when and at what location two devices can converse with each other, effectively linking the two systems, regardless of their operating systems or respective languages.

One good example of an API you will have encountered is the social media login. When a user attempts to login to their account, they can vouch for their identity via a third-party service such as Apple, Facebook, or Google. When a user chooses this option, the API acts to pass on the relevant data to the social media site, and so authenticating the client’s login request.

A single click or a fingerprint scan facilitates this, rather than the user having to enter information manually into several fields.

This API request–response exchange allows for communication between apps, and so for businesses to offer multiple services and experiences, without the necessity of having to create the functionality for the user from scratch every time.

The use of APIs is now ubiquitous. When you go to a business’s website and see its location on an inset Google map, this is because the business has installed an API on their page that allows Google to send the location data you need. Your desktop might have live information about the weather today, and that’s because your operating system is communicating with a weather app via an API to allow the presentation of this data for your convenience.


What is the API-first approach?


First class citizens

As suggested by the name, API-first is a development process that treats the API as the central and most core part of a potential application. Initial work focuses on the API before anything else is planned or prepared. It is for this reason that APIs are referred to as “first class citizens.”

This is distinct from the “code-first” approach that has developers create the application first and then insert an API at the end of the process. This kind of development process limits the ability of the app to access data across a raft of new and upcoming applications, and therefore limits the reach, functionality, and longevity.


APIs as communication tools

API-first development treats the API as foundational—the API is the first thing that is created and its design and functionality is determined by the business aims and needs of the app. This has the aim of allowing the eventual app to be able to communicate with as many other apps and services as possible over the longest possible length of time.

This ability to continue to communicate with other components over time is key to the API-first development approach. When new functionality or features are required, developers can create these as and when needed, fitting them around the central API that has already been created.


Contracts and documentation

This requires an API contract that is completely clear, and so accessible by other developers and software teams. This API contract denotes the documentation necessary for development teams to follow, and so create the API and work with the app later down the line. It contains information as to coding procedures and the language employed.

Good documentation with an appropriate API style guide is necessary so that different development teams across different time zones are able to not only collaborate with each other as and when necessary but also to work separately.

Once a sufficient standard of documentation is attained, then the app can be built and modified around the API, without the need for major coding or rewriting: the API-first approach removes this burden.


Client consultation and feedback

An integral part of API-first is to thoroughly consult with the client as to the business needs of their project, and so determine which are the best functions and services that should be offered by their app.

This allows for the design of an API contract and mock APIs before coding on the app itself has even begun. This ensures that the resulting API around which everything is built can meet the requirements of the client’s project, and the early testing and error handling made possible during this API design process also allows for the quick avoidance of initial design flaws.

The API in an API-first approach is thus unique to the customer and can be matched with their future applications and projects.


Monolith or microservice?

“Monolithic” architecture is usually an example of the previously mentioned ”code-first” development approach distinct from API-first. Here, software development is centered on the functions, data, and events being run through a single unit, as opposed to several different independent service units known as microservices.

The advantages and disadvantages of monolith versus microservice architecture is an ongoing conversation. However, given that an API-first strategy holds that functions and services can be added later as and when necessary, the API-first approach lends itself to the microservice infrastructure.

This is because the underlying functionality of the API-first approach mirrors the microservice construction of discrete units that are responsible for their own functions. These discrete units can also be multiple APIs that make the app larger and more flexible.

This is opposed to the monolithic approach of everything being contained and coded into one system, which can lead to issues with operability if even one small change is made. This is definitely not a problem in the API-first design.

Monolithic architecture also relies on one development team that is sufficiently familiar with the monolith to be able to work with it.

As noted, API-first architecture allows different developer teams to work on different parts of the project during application development. This is because they are actually working with a distinct microservice, mediated by the original API design carried out during the initial development stage after lengthy consultation with the client.

In summary then, an API-first approach:

  • Allows the client to specify exactly what they are hoping to achieve and what their precise business needs are.
  • Takes business objectives to create the API contract, which is maintained through clear and replicable API documentation that allows other knowledgeable developers to work on individual functions and components whenever necessary.
  • Entails the survival and maintenance of the app via the core API, which becomes a unique company resource.


Advantages of API-first

Given the summary of the API-first approach, we can look more closely at the specific advantages.

  • API-first means that the developer experience is improved significantly: because teams can work on different parts of the app in isolation, they are able to work independently and error test key functions without interfering with other teams or other APIs.
  • The API design coheres to the guidelines contained in the API documentation with a clear style guide. This allows teams to easily integrate APIs and other components without it affecting the consistency of the whole.
  • The API-first approach means that the API design is carried out with thorough consultation with the client before anything else even happens. This approach to software design saves on negative client feedback as the project progresses.
  • The early API design stage allows for early error testing and other troubleshooting, and completing the API design first means that it is also possible to check early on how all of the disparate elements work together, guaranteeing fast integration with minimum issues.
  • API-first design allows for the creation of multiple applications, even if only a single API is employed. With documentation based on a clear style guide, API governance carried out by a strong team can therefore create sophisticated apps with multiple functions.
  • The time saved by the above considerations results in quicker implementation times for each element from developers and therefore a quicker time to market.
  • Rest APIs allow for the assurance that components will be immediately functional on the web across different platforms and operating systems, including mobile devices.


Business benefits of API-first development

Some of the advantages involved in creating API-first platforms directly benefit the client. This is due to some specific features involved with this approach to building APIs for apps.

  • The existence of the consistent and reusable APIs involved with this approach means that the project can have a measurable legacy effect and act as an investment into the company’s future. This is because the API design first approach assumes the longevity of the project, and so the API-first approach is centered on flexibility and the ability to add functions to the app whenever necessary.
  • API-first also saves on development costs. The features of the app don’t have to be designed sequentially or in a way that makes them dependent on each other, as with monolithic architecture. This means that teams can work at their own pace, which can save significantly on development time.
  • Reusable APIs mean that multiple apps and other projects can be built on the initial components created by developer teams and the client. Companies then have a core tool that they can exploit for further business opportunities. This also represents significant savings in development costs.
  • Because the API is core to the app, it is the foundation around which all processes are based. This offers unprecedented scalability as new functions need only be integrated and delivered as micro frontends. It also makes troubleshooting easier, and the quality of the documentation makes it easier for any team to engage with the project at any future time.


In summary

It should be clear from the above that, like the microservice architecture it mirrors, the API-first approach is extremely agile and responsive to changes and needs as they arise.

Additional functionality and project revisions can simply be plugged into the core APIs, rather than significant revisions having to be applied to one single unit with attendant cross-cutting concerns.

Also, the mock APIs involved in the initial extensive planning and design stage with the client allow for the possibility of more feedback from the client, which in turn allows for earlier testing and evaluation, bringing the business the benefit of accelerated time-to-market.

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