Your Guide to Effective API Development: How to Build an API

API is by no means a new software concept. Even non-tech people are becoming increasingly aware of the benefits and potential of the API technology, not to mention the millions of users who use APIs daily without even knowing about it. With 1.29 billion API requests created in just six months, it’s clear that APIs are a force to be reckoned with when it comes to modern software.

And while APIs possess a lot of advantages for users, who can enjoy more diverse and functional software, this technology also delivers numerous benefits to software developers. But how exactly do you join the booming API market, what should you know before venturing into it, and how much does it all cost? Get the answers to these questions and more from our guide.

What Is an API?

The term API stands for Application Programming Interface and can be defined as a set of protocols, guidelines, and requirements for a software product to employ another software product, platform, or device, to provide better services to the users. APIs have become an integral part of software development these days, allowing companies to dramatically improve the functionality and appeal of their software products via API use.

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“API development is essential in building modern, interconnected applications that are scalable, secure, and user-friendly.”

Mykola Pyvovarov, Delivery Manager, QArea

Types of APIs

To fully understand the API and its place in the modern software development landscape, let’s start with the basics: the types of APIs and what they all entail when it comes to custom API development.

By Release Policy

1. Private APIs

Private, or internal APIs, are the type of APIs that are developed, maintained, and used only within a single company. These APIs are typically employed for cross-team communication and data exchange. Since a private API and its code are not available to the public, this helps keep the solution secure and scalable and the process of API management streamlined.

2. Public APIs

Public APIs, also known as external or open APIs, are APIs that are created and distributed by the company openly and are available for anyone to use. Due to the fact that an open API is available publicly and does not require significant authentication from its users, this type of APIs usually does not deal with the most sensitive data. At the same time, a public API can benefit its company a lot by promoting its services to a wide audience.

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“If you develop an API that can be used by another vendor or service, you should be confident that you provide well-documented and well-tested endpoints. A public API should also be secure, scalable, and easy for developers to integrate, ultimately driving the success and adoption of your service.”

Mykola Pyvovarov, Delivery Manager, QArea

3. Partner APIs

Partner APIs are distributed externally, but, unlike public APIs, the company behind the API is fully in control over who can use the API and for what purposes. For example, if you want third-party entities to access your API but want to make sure its use does not negatively reflect on your company, you can introduce a request procedure, prompting potential users to state how they are going to use your API.

4. Composite APIs

Composite APIs combine several APIs and can be used to handle API requests from different sources using just one software solution. An alternative use for a composite API is to perform a sequence of API calls without the need for human intervention. Implementing composite APIs reduces the load on the API server and helps process requests faster, resulting in a more effective use of the API traffic.

By Architecture

1. REST APIs

A REST API, also known as a RESTful API, where REST stands for Representational State Transfer, is currently the most popular type of API when it comes to their architecture. REST API development follows REST principles, which include client-server separation, layered systems, cacheable resources, and a uniform interface that is based on HTTP methods. REST APIs are highly valued by API developers thanks to their scalability, simple logic, and compatibility with modern web development standards.

2. SOAP APIs

SOAP API architecture (SOAP stands for Simple Object Access Protocol) is based on the protocol for exchanging information across entities and networks. SOAP APIs are considered to have a more structured, clearly defined approach to data transmission and are widely used to create APIs for a more formal use. SOAP APIs also stand out for their impeccable security and working with all communication protocols, not just HTTP.

3. GraphQL APIs

GraphQL is a query language and a server-side runtime used to create APIs that require data from multiple sources for their operation, as a single API endpoint can be used to process all kinds of data without any delays. GraphQL APIs stand out for their flexibility and adaptability. They are considered to be an excellent option for building single page applications, third-party integrations, and solutions with complex data requirements.

4. WebSocket APIs

WebSocket is a technology used in web API development to create a stable, long-term, bidirectional connection between the client and the server. The efficient performance of WebSocket APIs and the strength of the connection they provide make them a popular choice for products that require real-time data updates, such as online chats, multiplayer games, and Internet of Things applications.

5. gRPC APIs

gRPC is a high-performance Remote Procedure Call framework that was originally launched and developed by Google. gRPC supports multiple programming languages and can run in any environment. It uses Protocol Buffers (Protobuf) for data serialization and operates over HTTP/2, which enables features like multiplexing. The service definition describes the available methods on the server and the parameters required.

6. MQTT APs

MQTT, or Message Queueing Telemetry Transport, is an OASIS standard messaging protocol widely used in API development, among other things. It is designed to be lightweight, making it suitable for low-bandwidth, high-latency networks. Clients subscribe to topics to receive messages, a feature that is commonly utilized in IoT (Internet of Things) for sending data between devices.

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How Does an API Work?

Understanding the nature of API thoroughly and completely is a crucial step for venturing into the API business as a provider. So, how does an API system work and which characteristics make an API such a popular choice for software development right now? Let’s delve deeper into the logic of API solutions.

At its essence, an API serves as the communication method between two endpoints: the server and the client-facing application. A common example of how an API works is the process of booking a hotel room on one of the many aggregator sites. After you enter your desired stay details, the system comes up with a list of available options in a matter of seconds. This is carried out via an API, which transfers data from multiple sources (in this case, hotels) to display them all in one convenient interface.

The work of an API can be broken down into five essential steps:

  1. The client application sends a request to the API, and the request is formatted according to the structure requirements of the API.
  2. The API receives the request after checking whether it conforms to the necessary protocols and requirements; authorization may also be needed at this point.
  3. The API processes the request after a successful authorization, retrieving data from the required sources, performing calculations, or sending requests to other services.
  4. The API issues a response, where the necessary data is formatted according to the requirements of the API and the client application.
  5. The client application receives the response and displays it in the predefined format, where the user can take further action.

Benefits of API Development: Why Build an API Right Now

With 57% of the web traffic coming from APIs, it’s clear that the API economy is booming and that now is the perfect time to jump on this train. However, in addition to the clear revenue increase potential that is linked to API development and integration, the decision to create a bespoke API has a number of other significant benefits.

Streamlined Collaboration

On average, an enterprise works with 1,295 cloud services, and that number continues to grow year after year. More importantly, most of these services use API technology to build secure and stable connections. These connections are typically implemented throughout the organization, giving teams an effective and accessible way to collaborate on projects and exchange vital information. Plus, extensive API documentation that typically comes with active API use further encourages the collaborative and knowledge sharing processes within the company.

Spreading Innovation

Whether you create an API for your business to use internally or want to make your API available for other companies to use, this is the technology that has been at the forefront of innovation for the past few years. Different API products allow businesses to add the desired functionality with far less coding effort compared to traditional software development. This way, when exchanging APIs, businesses spread innovation across the industry, helping each other become more competitive and achieve long-term user appeal.

Efficient Monetization

While it costs money to create an API, in most cases, the API makes money for its owner in return. This can happen indirectly — for example, when an airline creates an API and encourages API usage across various aggregator sites and booking services, the increase in sales makes the API development efforts worthwhile. However, APIs can also be monetized directly by providing paid access to the API for other companies, typically through the subscription option.

Unparalleled Flexibility and Scalability

Customized API development is arguably the fastest way to add new features without embarking on a months-long process of traditional application development. Plus, integrating a ready-made API into the system costs even less than building an API from scratch. This is a highly effective way of keeping up with the changing market demands. Moreover, APIs allow the business to quickly scale its operations and accommodate a growing number of users or requests with minimal effort and waiting time.

Enhanced Business Intelligence

Businesses have to make numerous crucial decisions every day, and those decisions only work in the favor of the business when they are based on precise data instead of guesses and assumptions. API allows companies to gather data from various sources, including CRM and ERP software, social media platforms, website analytics tools, and market analysis solutions, transforming raw data into easily digestible reports that help businesses make informed decisions that positively shape their future.

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Key Features to Include In Your API Design

Any guide to API development will tell you that an API should meet a set of criteria in order to be successful. Specifically, an API needs to be consistent in its design, have outstanding reliability, and provide scalability and flexibility so that the development team can easily adjust it to the changing business needs of the company.

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“When you are designing API, focus on non-functional requirements in addition to the functional ones: your API must be easily scalable, fault-tolerant and secure; it needs to be easily integrated with a mobile client; the technological stack of your API needs to remain up-to-date for at least three years after the launch.”

Mykola Pyvovarov, Delivery Manager, QArea

However, API development best practices also include several features that customers and developers expect to see in pretty much any API product. Here are the most important features that enhance API design and development.

Authentication and Authorization

Authentication and authorization are two different things (authentication is responsible for identifying the users, while authorization deals with granting access to certain parts of the API), but both are equally important for maintaining the optimal security of the solution without putting extra strain on the development team. Popular technologies for implementing authentication and authorization include OAuth, OAuth 2, and JWT.

Pagination

The work of an API is closely linked to databases, which tend to expand over time as there is more data for them to process and to store. With time, you can notice the API performance slowing down, and it often happens due to the solution finding it harder to retrieve certain sets of data. Pagination is a technique designed to help with this issue. Pagination helps an API efficiently figure out how much data should be retrieved and displayed and how often it should happen.

Caching

Caching is another technique that increases the API efficiency and speed without introducing any drastic changes to its architecture. Caching means speeding up the retrieval of the necessary resources by preparing and storing data in an in-memory database. With the use of this technique, each request takes less to process, which allows the information to be delivered and displayed faster and ensures your API continues to perform well.

Search by Criteria

Allowing users to search and retrieve data by specific criteria significantly speeds up the operation of the API and improves the accuracy of information transferred through the API. The most popular way to sort and search data is by date because date-related changes (when the data was created, modified, and used) are the first ones to come up whenever a change is considered. This is also referred to as modification timestamps.

JSON Support

This feature is not mandatory, but given how many API developers now go for the REST architecture, making your API RESTful, or providing it with JSON support, can help you kill two birds with one stone. First, you will make it compatible with most API development tools and other software solutions that rely on JSON or a similar technology. Second, you will attract a wider audience to your product that consists of people who are already using JSON for other development activities and are, therefore, more likely to choose JSON-compatible APIs.

Having provided API development services for over a decade, we have built an impressive technological stack for creating functional, high-performance, scalable API products. Our findings include API tools that are specific to these software products, as well as technologies and programming languages widely used in other segments of software development. For the latter, we use the following:

  • Laravel, Sencha, and CakePHP for PHP-based APIs
  • Express for Node.js, Next for React.js, and Nuxt for Vue.js when it comes to JavaScript frameworks and libraries
  • Spring or Spring Boot for Java-based APIs
  • .NET Core or .NET MVC for C# in API development
  • Gin or Echo for products developed on Go

Now, when it comes to standalone tools used specifically for API development, there is no shortage of those either. These are the tools that are now widely used to create API products:

  • Apigee. Apigee is an API management platform that is now available as part of the Google Cloud solution. Apigee allows developers to create APIs using robust visual tools and helps build inter-connected software products for better synergy.
  • AWS API Gateway. This is a full-cycle Amazon Web Services platform for building, publishing, and maintaining APIs on any scale. Like many AWS offerings, API Gateway provides a serverless architecture, so users can build APIs without also managing the infrastructure. 
  • Apiary. Apiary, which is now offered as part of Oracle’s API Platform Cloud Service, is the go-to tool for creating APIs using the API Blueprint format. This tool supports a variety of integrations with third-party platforms and provides a mock server for efficient prototyping and testing.
  • Apidog. This is a tool that was created to simplify and streamline the API design and documentation process, two activities that normally require a lot of time and effort from the team. Apidog supports real-time collaboration and provides a handy visual editor for design.
  • Swagger. Swagger, which is now known as OpenAPI, is one of the most popular platforms for designing, developing, documenting, and testing APIs. It comes with a comprehensive selection of features and an appealing visual interface, which makes it easy and engaging to use.
  • API Blueprint. API Blueprint is a markdown-based language that focuses on simplicity and readability, making it an excellent choice for straightforward API design and documentation. This tool integrates with several handy tools, including Aglio, which converts API Blueprint files into visually appealing documentation, and Dredd, which tests your API against the API Blueprint specification to ensure accuracy and compliance.
  • Postman. Postman is a well-known and widely used tool primarily recognized for its API testing capabilities, but it also provides robust features for API design, documentation, and monitoring. With Postman, users can define APIs directly within the platform, making it a one-stop solution for API lifecycle management.

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API Development Process: How to Build Your API

It’s not always easy to define the API development process in strict terms or rules because each project is unique, as is the product it delivers. Still, most API development projects follow a certain sequence of steps to ensure a strong end result. Here are the steps you need to take to develop a powerful API solution.

1. Discovery Phase

At the first stage of the development process, the project stakeholders and the development team need to identify the goals of the project, the target audience, and the scope of functionality the product is intended to offer. For this phase to be successful, the team needs to have a complete understanding of who the product is for and what users want to see in a new API. This helps define and flesh out the requirements, both functional and non-functional, to make sure that every minute of the development process is spent on creating a product the audience will actually want to use.

2. API Design and Architecture

This is the stage where the previously discussed functionality gets translated into the actual API design, which is implemented according to the findings obtained during the discovery phase. The team may use any combination of the tools and technologies we have listed above or come up with their own tech stack that matches the goals of the project. However, it is integral to choose an API design and architecture that meets the following criteria:

  • Usability. The software product should have all the functionality originally intended, and the functionality should be easily accessible for developers to use.
  • Reliability. The product needs to have as little downtime as possible and support any number of users or requests without disrupting the performance.
  • Scalability. In order to keep up with the changes in demand, the API needs to be able to quickly scale up or down without costing the team days of development efforts.
  • Security. The API needs to be thoroughly protected against malicious attacks: the security gaps need to be identified and fixed before they can do any real damage to the user data or product reputation.
  • Testability. The software solution needs to be readily available for all kinds of testing activities, both unit tests conducted by the development team and other checks left to the testing team.

3. API Development

The development stage may be the most crucial stage of developing an API, as the outcome of this stage will impact the success of the entire project. However, it’s only possible for the development phase to go right when the previous stages have been completed diligently and in full. If that’s the case, then the team will have everything they need, including the requirements, tech stack, and roles, for the process to be smooth and effective.

Currently, the best way to conduct a development process is to use the Agile project methodology, as it allows to plan an incremental delivery process. The team will be able to quickly evaluate the results of the latest development stretch, make changes if necessary, and test the updated solution right away to catch the bugs as early as possible. It’s also crucial to create comprehensive documentation as the project progresses.

4. API Testing

In the modern API development landscape, testing is as important as development. Testing the product in full and starting with the early development stages is the only way to make sure that major bugs don’t make it into the production, where they can threaten the security and stability of the product, user experience, and, eventually, the reputation of the product on the market. A little later in this article, we are going to talk about testing APIs and automating API testing for better results.

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“Cover all your endpoints with unit tests. Check not only the functional logic but also the boundary values of the transmitted parameters and errors that may occur during calculations. Your service must be able to handle and log all exceptional situations. Before the release, conduct load and stress testing of your API to understand its throughput.”

Mykola Pyvovarov, Delivery Manager, QArea

5. Post-Deployment Activities

Once the API is deployed, the work of the development team is far from being over. Their next task, and one that can take months, if not years, is monitoring the state of the application after the deployment and introducing the necessary changes in case the product needs tweaking. Some of the most common metrics to monitor include:

  • Uptime
  • Response time
  • Monthly users
  • Monthly requests
  • Memory usage

There are also some business and financial metrics, such as monthly revenue, but those are usually not included in the scope of tasks of the development team. The team may also use certain tools like Postman Monitoring and Amazon CloudWatch to track the state of the API in real time and instantly see what needs to be corrected.

API Testing: Why and How to Test Your API

It is absolutely impossible to release a high-quality, durable software solution without comprehensive rounds of testing — it’s why we have quality assurance in the first place. Testing is also integral to the realm of API development, although it stands out from the process of testing other software solutions for several reasons.

First, even a simple API needs to be tested thoroughly because it’s going to interact with numerous other software products that can