This article is an excerpt from the book, "Building an API Product", by Bruno Pedro. Build cutting-edge API products confidently, excelling in today's competitive market with this comprehensive guide on API fundamentals, inner workings, and steps for successful API product development.Introduction The life of an API product consists of a series of stages. Those stages form a cycle that starts with the initial conception of the API product and ends with the retirement of the API. The name of this sequence of stages is called a life cycle. This term started to gain popularity in software and product development in the 1980s. It’s used as a common framework to align the different participants during the life of a software application or product. Each stage of the API life cycle has specific goals, deliverables, and activities that must be completed before advancing to the next stage. There are many variations on the concept of API life cycles. I use my own version to simplify learning and focus on what is essential. Over the years, I have distilled the API life cycle into four easy-to-understand stages. They are the design, implementation, release, and maintenance stages. Keep reading to gain an overview of what each of the stages looks like. Figure 4.1 – The API life cycle The goal of this chapter is to provide you with a global overview of what an API life cycle is. You will see each one of the stages of the API life cycle as a transition and not simply an isolated step. You will first learn about the design stage and understand how it’s foundational to the success of an API product. Th en, you’ll continue o n to the implementation stage, where you’ll learn that a big part of an API server can be generated. After that, the chapter explores the release stage, where you’ll learn the importance of finding the right distribution model. Finally, you’ll understand the importance of versioning and sunsetting your API in the maintenance stage. After reading the chapter, you will understand and be able to recognize the API life cycle’s diff erent stages. You will understand how each API life cycle stage connects to the others. You will also know the participants and stakeholders of each stage of the API life cycle. Finally, you will know the most critical aspects of each stage of the API life cycle. In this article, you’ll learn about the four stages of the API life cycle: Design Implement Release Maintain Design The first stage of the API life cycle is where you decide what you will build. You can view the design stage as a series of steps where your view of what your API will become gets more refined and validated. At the end of the design stage, you will be able to confidently implement your API, knowing that it’s aligned with the needs of your business and your customers. The steps I take in the design stage are as follows: Ideation Strategy Definition Validation Specification These steps help me advance in holistically designing the API, involving as many different stakeholders as possible so I get a complete alignment. I usually start with a rough idea of what the ideal API would look like. Then I start asking different stakeholders as many questions as possible to understand whether my initial assumptions were correct. Something I always ask is why an API should be built. Even though it looks like a simple question, its answer can reveal the real intentions behind building the API. Also, the answer is different depending on whom you ask the question. Your job is to synthesize the information you gather and document pieces of evidence that back up the decisions you make about the API design. You will, at this stage, interview as many stakeholders as possible. They can include potential API users, engineers who work with you, and your company’s leadership team. The goal is to find out why you’re building the API and to document it. Once you know why you’re building the API, you’ll learn what the API will look like to fit the needs of potential users. To learn what API users need, identify the personas you want to serve and then put yourself in their shoes. You’ve already seen a few proto-personas in Chapter 2. In this API life cycle stage, you draw from those generic personas and identify your API users. You then contact people representing your API user personas and interview them. During the interviews, you should understand their JTBDs, the challenges they face during their work, and the tools they use. From the information you obtain, you can infer the benefits they would get from the API you’re building and how they would use the API. This last piece of information is critical because it lets you define the architectural style of the API. By knowing what tools your user personas use daily, you can make an informed decision about the architectural style of your API. Architectural styles are how you identify the technology and type of communication that the API will use. For example, REST is one architectural style that lets API consumers interact with remote resources by executing one of the HTTP verbs. Among those verbs, there’s one that’s natively supported by web browsers—HTTP GET. So, if you identify that a user persona wants to use a web browser to consume your API, then you will want to follow the REST architectural style and limit it to HTTP GET. Otherwise, that user persona won’t be able to use your API directly from their tool of choice. Something else you’ll want to define is the capabilities your API will offer users. Defining capabilities is an exercise that combines the information you gathered from interviews. You translate JTBDs, benefits, and behaviors into a set of capabilities that your API will have. Ideally, those capabilities will cover all the needs of the users whom you interviewed. However, you might want to prioritize the capabilities according to their degree of urgency and the cost of implementation. In any case, you want to validate your assumptions before investing in actually implementing the API. Validation of your API design happens first at a high level, and after a positive review, you attempt a low-level validation. High-level validation involves sharing the definition of the architectural style and capabilities that you have created with the API stakeholders. You present your findings to the stakeholders, explain how you came up with the definitions, and then ask for their review. Sometimes the feedback will make you question your assumptions, and you must refine your definitions. Eventually, you will get to a point where the stakeholders are all aligned with what you think the API should be. At that point, you’re ready to attempt a low-level validation. The difference between a high-level and a low-level validation is the amount of detail you share with your stakeholders and how technical the feedback you expect needs to be. While in high-level validation, you mostly expect an opinion about the design of the API, in low-level validation, you actually want the stakeholders to test the API before you start building it. You do that by creating what is called an API mock server. It allows anyone to make real API requests to a server as if they were making requests to the real API. The mock server responds with data that is not real but has the same shape that the responses of the real API would have. Stakeholders can then test making requests to the mock server from their tools of choice to see how the API would work. You might need to make changes during this low-level validation process until the stakeholders are comfortable with how your API will work. After that, you’re ready to translate the API design into a machine-readable definition document that will be used during the implementation stage of the API life cycle. The type of machine-readable definition depends on the architectural style identified earlier. If, for example, the architectural style is REST, then you’ll create an OpenAPI document. Otherwise, you will work with the type of machine-readable definition most appropriate for the architectural style of the API. Once you have a machine-readable API definition, you’re ready to advance to the implementation stage of the API life cycle. Implementation Having a machine-readable API definition is halfway to getting an entire API server up and running. I won’t focus on any particular architectural style, so you can keep all options open at this point. The goal of the machine-readable definition is to make it easy to generate server code and configuration and give your API consumers a simple way to interact with your API. Some API server solutions require almost no coding as long as you have a machine-readable definition. One type of coding you’ll need to do—or ask an engineer to do—is the code responsible for the business logic behind each API capability. While the API itself can be almost entirely generated, the logic behind each capability must be programmed and linked to the API. Usually, you’ll start with a first version of your API server that can run locally and will be used to iteratively implement all the business logic behind each of the capabilities. Later, you’ll make your API server publicly available to your API consumers. When I say publicly available, I mean that your API consumers should be able to securely make requests. One of the elements of security that you should think about is authentication. Many APIs are fully open to the public without requiring any type of authentication. However, when building an API product, you want to identify who your users are. Monetization is only possible if you know who is making requests to your API. Other security factors to consider have already been covered in Chapter 3. They include things such as logging, monitoring, and rate limiting. In any case, you should always test your API thoroughly during the implementation stage to make sure that everything is working according to plan. One type of test that is particularly useful at this stage is contract testing. This type of test aims to verify whether the API responses include the expected information in the expected format. The word contract is used to describe the API definition as something that both you—the API producers—and your consumers agree to. By performing a contract test, you’ll verify whether the implementation of the API has been done according to what has been designed and defined in the machine-readable document. For example, you can verify whether a particular capability is responding with the type of data that you defined. Before deploying your API to production, though, you want to be more thorough with your testing. Other types of tests that are well suited to be performed at this stage are functional and performance testing. Functional tests, in particular, can help you identify areas of the API that are not behaving as functionally as intended. Testing different elements of your API helps you increase its quality. Nevertheless, there’s another activity that focuses on API quality and relies on tests to obtain insights. Quality assurance, or QA, is one type of activity where you test your API capabilities using different inputs and check whether the responses are the expected ones. QA can be performed manually or automatically by following a programmable script. Performing API QA has the advantage of improving the quality of your API, its overall user experience, and even the security of the product. Since a QA process can identify defects early on during the implementation stage of an API product, it can reduce the cost of fi xing those defects if they’re found when consumers are already using the API. While contract and functional tests provide information on how an API works, QA off ers a broader perspective on how consumers experience the API. A QA process can be a part of the release process of your API and can determine whether the proposed changes have production quality. Release In soft ware development, you can say that a release happens whenever you make your soft ware available to users. Diff erent release environments target diff erent kinds of users. You can have a development environment that is mostly used to share your soft ware with other developers and to make testing easy. Th ere can also be a staging environment where the soft ware is available to a broader audience, and QA testing can happen. Finally, there is a production environment where the soft ware is made available generally to your customers. Releasing soft ware—and API products—can be done manually or automatically. While manual releases work well for small projects, things can get more complicated if you have a large code base and a growing team working on the project. In those situations, you want to automate the release as much as possible with something called a build process. During implementation, you focus on developing your API and ensuring you have all tests in place. If those tests are all fully automated, you can make them run every time you try to release your API. Each build process can automatically run a series of steps, including packaging the soft ware, making it available on a mock server, and running tests. If any of the build steps fail, you can consider that the whole build process failed, and the API isn’t released. If the build process succeeds, you have a packaged API ready to be deployed into your environment of choice. Deploying the API means it will become available to any users with access to the environment where you’re doing the release. You can either manage the deployment process yourself, including the servers where your API will run, or use one of the many available API gateway products. Either way, you’ll want to have a layer of control between your users and your API. If controlling how users interact with your API is important, knowing how your API is behaving is also fundamental. If you know how your API behaves, you can understand whether its behavior is aff ecting your users’ experience. By anticipating how users can be negatively aff ected, you can proactively take measures and improve the quality of your API. Using an API monitor lets you periodically receive information about the behavior and quality of your API. You can understand whether any part of your API is not working as expected by using a solution such as a Postman Monitor. Diff erent solutions let you gather information about API availability, response times, and error rates. If you want to go deeper and understand how the API server is performing, you can also use an Application Performance Monitor (APM). Services such as New Relic give you information about the performance and error rate of the server and the code that is running your API. Another area that you want to pay attention to during the release stage of the API life cycle is documentation. While you can have an API reference automatically built from your machine-readable defi nition, you’ll want to pay attention to other aspects of documentation. As you’ve seen in Chapter 2, good API documentation is fundamental to obtaining a good user experience. In Chapter 3, you learned how documentation can enhance support and help users get answers to their questions when interacting with your API. Documentation also involves tutorials covering the JTBDs of the API user personas and clearly showing how consumers can interact with each API feature. To promote the whole API and the features you’re releasing, you can make an announcement to your customers and the community. Announcing a release is a good idea because it raises the general public’s awareness and helps users understand what has changed since the last release. Depending on the size of your company, your available marketing budget, and the importance of the release, you choose the media where you make the announcement. You could simply share the news on your blog, or go all the way and promote the new version of your API with a marketing campaign. Your goal is always to reach the existing users of your API and to make the news available to other potential users. Sharing news about your release is a way to increase the reach of your API. Another way is to distribute your API reference in existing API marketplaces that already have their own audience. Online marketplaces let you list your API so potential users can fi nd it and start using it. Th ere are vertical marketplaces that focus on specifi c sectors, such as healthcare or education. Other marketplaces are more generic and let you list any API. Th e elements you make available are usually your API reference, documentation, and pointers on signing up and starting to use the API. You can pick as many marketplaces as you like. Keep in mind that some of the existing solutions charge you for listing your API, so measure each marketplace as a distribution channel. You can measure how many users sign up and use your API across the marketplaces where your API is listed. Over time, you’ll understand which marketplaces aren’t worth keeping, and you can remove your API from those. Th is measurement is part of API analytics, one of the activities of the maintenance stage of the API life cycle. Keep rea ding to learn more about it. Maintenance You’re now in the last stage of the API life cycle. This is the stage where you make sure that your API is continuously running without disturbances. Of all the activities at this stage, the one where you’ll spend the most time will be analyzing how users interact with your API. Analytics is where you understand who your users are, what they’re doing, whether they’re being successful, and if not, how you can help them succeed. The information you gather will help you identify features that you should keep, the ones that you should improve, and the ones that you should shut down. But analytics is not limited to usage. You can also obtain performance, security, and even business metrics. For example, with analytics, you can identify the customers who interact with the top features of your API and understand how much revenue is being generated. That information can tell you whether the investment in those top features is paying off. You can also understand what errors are the most common and which customers are having the most difficulties. Being able to do that allows you to proactively fix problems before users get in touch with your support team. Something to keep in mind is that there will be times when users will have difficulties working with your API. The issues can be related to your API server being slow or not working at all. There can be problems related to connectivity between some users and your API. Alternatively, individual users can have issues that only affect them. All these situations usually lead to customers contacting your support team. Having a support system in place is important because it increases the satisfaction of your users and their trust in your product. Without support, users will feel lost when they have difficulties. Worse, they’ll share their problems publicly without you having a chance to help. One situation where support is particularly requested is when you need to release a new version of your API. Versioning happens whenever you introduce new features, fix existing ones, or deprecate some part of your API. Having a version helps your users know what they should expect when interacting with your API. Versioning also enables you to communicate and identify those changes in different categories. You can have minor bug fixes, new features, or breaking changes. All those can affect how customers use your API, and communicating them is essential to maintaining a good experience. Another aspect of versioning is the ability to keep several versions running. As the API producer, running more than one version can be helpful but can increase your costs. The advantage of having at least two versions is that you can roll back to the previous version if the current one is having issues. This is often considered a good practice. Knowing when to end the life of your entire API or some of its features is a simple task, especially when there are customers using your API regularly. First of all, it’s essential that you have a communication plan so your customers know in advance when your API will stop working. Things to mention in the communication plan include a timeline of the shutdown and any alternative options, if available, even from a competitor of yours. A second aspect to account for is ensuring the API sunset is done according to existing laws and regulations. Other elements include handling the retention of data processed or generated by usage of the API and continuing to monitor accesses to the API even after you shut it down. ConclusionAt this point, you know how to identify the different stages of the API life cycle and how they’re all interconnected. You also understand which stakeholders participate at each stage of the API life cycle. You can describe the most important elements of each stage of the API life cycle and know why they must be considered to build a successful API product. You first learned about my simplified version of the API life cycle and its four stages. You then went into each of them, starting with the design stage. You learned how designing an API can affect its success. You understood the connection between user personas, their attributes, and the architectural type of the API that you’re building. After that, you got to know what high and low-level design validations are and how they can help you reach a product-market fit. You then learned that having a machine-readable definition enables you to document your API but is also a shortcut to implementing its server and infrastructure. Afterward, you learned about contract testing and QA and how they connect to the implementation and release stages. You acquired knowledge about the different release environments and learned how they’re used. You knew about distribution and API marketplaces and how to measure API usage and performance. Finally, you learned how to version and eventually shut down your API. Author BioBruno Pedro is a computer science professional with over 25 years of experience in the industry. Throughout his career, he has worked on a variety of projects, including Internet traffic analysis, API backends and integrations, and Web applications. He has also managed teams of developers and founded several companies, including tarpipe, an iPaaS, in 2008, and the API Changelog in 2015. In addition to his work experience, Bruno has also made contributions to the API industry through his written work, including two published books on API-related topics and numerous technical magazine and web articles. He has also been a speaker at numerous API industry conferences and events from 2013 to 2018.
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