What is API Design? API Design Best Practices and Principals for APIs

Before any development is made on any structure or even product, there must be a well-established plan and well-informed decisions to ensure the product produces the desired functionalities. These decisions and plans make up the design process. Therefore, significant design decisions and planning lead to better outcomes. 

APIs are no different from any other standard product when it comes to the designing process. Web developers understand how the building process can end up in a web of tangled codes that do not offer the functionality required. That is why the first stages of building an application programming interface are crucial. API design is the process of building an intermediary interface for a system-to-system connection to expose data to application users and developers. 

The fundamental API design influences how well users can consume it and the general user experience. This development [process does not allow a single approach. Instead, it combines a series of guidelines to meet initial expectations and continue to work consistently. Application programming interface designers closely follow industry best practices, design patterns, API design principles, and user needs to develop software that presents excellent functionality.

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The Design Process

Years back, the standard APIs were SOAP; nowadays, the most popular design style is REST, a resource-based design architecture. Representational State Transfer (REST) was a proposal from Roy Fielding, independent of any underlying protocol. The REST API design allows various users to communicate with a server through the API. Apart from RESTful design, there are other architectural designs such as GraphQL. 

API design is a process that works around principles that have the user in mind. APIs can be compared to different car models; they differ in components to suit every user’s needs. But despite the differences, an experienced driver will quickly figure out how to drive different cars. With this analogy, API design processes create a platform that every user can access. The process follows these principles:

i. Defined Simplicity

The term simplicity in API design is not a standard method but depends on the context. For instance, a system may be simple for specific uses but problematic in others. Simplicity can revolve around development aspects like data formats, method structure, authentication, and usage policies.

Data formats define an API’s simplicity based on its ability to support XML, JSON, or a combination of formats. For instance, most are the preferred architectural design is REST API design, then the application should accept JSON requests and send responses to the same. Similarly, method structure depends on the sequence in which users will access data, whether it is specifically targeted requests or return to a broad set of data.

ii. API with flexibility

A simple-to-use API without flexibility runs the risk of being restrained to specific uses only. The API design process determines the scope of operations and the potential user space. The underlying systems and data models that the API is built on should be feasible and valuable to users. This helps find a balance between simplicity and flexibility. 

Developers focus on the business entity that the API exposes to develop a system that offers the required functionalities. For instance, of the API exposed e-commerce systems, then the primary entities are customers and orders.

In the API design process, there are vital questions that developers ask themselves to walk through the period of designing. Since this is a continuous process, there could be a need to update or change certain functionalities depending on the market requirements.

• Does the API support the use case? During the design, developers identify API users and must ensure that the platform supports these uses. This is where flexibility comes in, as discussed above, to include the most common use cases and the least frequent for continued growth. 
• Is RESTful architectural design necessary? As much as RESTful APIs are popular, developers do not have to go with the trend for its sake if it doesn’t suit the APIs’ use cases. There are other architectural styles like GraphQL, which may favor the API use cases.
• Does the API have a datacenter in target geographical locations? APIs are designed to be used by people who live in different regions of the world. In the designing process, developers should consider if they have covered areas with most of their users or target users.

API Design Best Practices

There are many best practices when it comes to designing treat APIs. Below are a few basic industry-level API Design best practices that developers follow for excellent outcomes: 

• Acceptance and response to JSON:  APIs should generally respond to JSON requests because almost every networked technology can use it. Other data formats may need changes when they land on frameworks that do not support them, for instance, XML. JSON is by far the most straightforward data format that allows data transfer on the interface without needing changes. For this to work, developers ensure that the endpoints return JSON as a response.
• Usage of nouns instead of verbs in endpoints: RESTful APIs are based on nouns; the endpoint is actioned based on nouns that directly identify the user entity.
• Plural nouns: Another best practice in API design is the naming of collections with plural nouns as they fit all endpoints. At some point, the argument is that users will send a request for multiple data and not always a single item. 
• Versioning: An API designer should understand businesses change, and the need for expansion presents itself. Therefore, versioning the API before it launches or releases it to the market is crucial. This can be done by using different URLs, accepting other headers, etc. 
• Documentation: Well-documented APIs save designers time and energy spent answering developer and user questions when navigation becomes difficult. An API that has been well documented contains attributes that define how it works and accessible on the web.
• Using HTTP methods: These are communications actions over the HTTP protocol that offer useful operations for the foundation of REST APIs. These include GET, POST, PUT, PATCH, and DELETE commands. 
• Using HTTP status codes: HTTP status codes are used to communicate errors and success. The most used HTTP status codes(https://stoplight.io/api-design-guide/basics/) are 200, 201, 401, 403, 404, and 500

API Design Patterns

 For designers, following API design principles and API design patterns is not complete without diving into the REST API design rulebook to pick some concepts that have worked for others or have been solved. Here are some common API design patterns.

•  Sorting: Consistent endpoint names are the way to go for a designer when choosing a default sort order. It can be a time-consuming process for API developers, but some users may need access to this function. Sort orders could be as simple as whether results should be ascending or descending to display by dates. Either way, sorting does not have to open an APIs entire database to users. Instead, owners decide which fields to enable through sorting.
•  Pagination: How do APIs with many data help users access request results in an orderly way? The answer is in paging, then allowing consumers to adjust pages to desired sizes. Paging also enables a user to send in a request for specific page results.
•  Filtering: API designers can use filter option patterns to help users narrow down the query results. For advanced filtering options, other API technologies like Graph QL offer more choices. 
•  Hypermedia links: Basically, linking helps users find what else is available concerning their search query. Hypermedia links can be useful in paging to link users to the next results.

Benefits of API Design

• Better Implementation:  An API Design is a driver of what the API wants to achieve and provides an overview of all the operations associated with endpoints. API owners who invest in effective design processes prevent complicated configurations and promote the core product’s proper implementation.
• Facilitates Development: API development is a continuous process, and the design sets the pace for any upcoming evolution or growth. A straightforward design ensures the development team knows which resources need updates and avoid repetitions.
• Better user experience: Developers want to work with APIs that make their work easier and not harder. When the design process has well-organized resources, intuitive interfaces, and great speed, users can efficiently work with the API. 

 APIs are used by different people, especially web developers and organizations that require an intermediary for their system to system connections. Common API users are mobile application developers, website developers, data scientists, and operations people.

 This group of people has expectations when using an API, and for designers, the API Design should have the following:

• Easy to read and work with
• Consistent and useful for developers
• Provide outstanding support to users and developers. This can result in documentation and FAQs.
• Support intended user cases and be flexible enough to be adopted by others.

Facebook’s API is not developer-friendly, and with frequent updates, their product deprecates and becomes even more complicated for hackers. Gmail also had a recent update to their API. Still, even though it was a welcome experience, users did not receive the faster speeds expected, especially those who consume many resources through the API. But both these APIs have a great user base.

Generally, for a new API designer, the luxury of an immediate large following may not be on the horizon. Therefore, working on a great API Design, whether RESTful or using other architectural designs, is critical in attracting developers and users. 

There is no single approach in the REST API design rulebook that will work for all organizations. That is why it is essential for API developers to tailor the design process according to use cases and make it flexible enough to be accessible to other interested parties. Consumer needs are the guiding light for building and designing great API.

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