What is API Integration and How Does it Work?

April 05, 2022 • 872 Views • 15 min read

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Tetiana Stoyko

CTO & Co-Founder

Despite the fact, that Custom API development is popular nowadays and can be met almost everywhere, most common users have no idea what it is and how exactly it works. Most of the features offered on websites or different third-party services, such as weather forecast, and in-app Google Maps navigation - are API integrations. So how did it happen, that such a widespread phenomenon is almost unknown?

The reason is that API is software, which works on the background level. This is why its structure is hidden from a regular user. At the same time, software developers are aware of API, knowing its features and benefits of API integration. So what is the custom API integration and why are API integration services important?

What is API Integration?

Application Programming Interfaces are used to simplify the work of development teams as well as to spread the ready-to-use product. Seamless API integration allows skipping the “development from scratch” stage, by creating links and connections between different apps or software solutions. Do not confuse the API with the Plugin, which is used as additional software to extend functionality as well.

Mostly API is used to integrate resource-intensive software applications, to save time and effort, trying to compete with it. For example, it is easier and faster for Uber to integrate Google Maps API into their app, instead of developing their alternative GPS-tracking systems.

Despite that, Google Maps API offers also a variety of other features such as routing or up-to-date place information. So, it is not just maps, but the combination of separate functionalities, which interact, creating a difficult ecosystem.

Google is a great example, which offers a lot of other popular and useful API integrations, such as Google Drive.

Different API development & integration solutions cover a wide range of spheres and propose various features, that can interact with each other. Moreover, companies like Google have all the needed resources to develop and update all these offers. As a great addition, Google apps are popular and well-known, thanks not only to the brand but to advertising and distribution plans.

For example, it uses mixed user levels of APIs and monetizes only a few of them. Such an approach improves the brand’s recognition, as the number of users increases, because such products are free for individual usage, but are paid for corporate usage. Such a strategy is called corporate API type of release policies. But what are other types and what is the difference?

Types of API Integrations

So, we already know a little about the corporate type and its specifics. Now let’s learn how can we divide API into different types.

By The Release Policies


This type is used for internal purposes. Usually it is created specifically for the corporation or organization and the main audience is corporation workers or departments. Such interfaces often are products of the companies, that develop them.

The private status does not always mean that they could not be integrated elsewhere except the corporation. Frankly, they could be distributed as the other systems or apps for the public, but the API descriptor document or interface itself will be available only for those users, who cooperate with the owner of the software. It helps the publisher to keep every business operation under its full control and makes it impossible for third parties to make changes or use all full functionalities of the API.


Unlike the private type or the corporate one, the public approach means that all the features and API descriptor documents are of free usage, no matter if it is an individual user or corporation that wants to integrate such API. Nonetheless, sometimes such software is available for a small fee, such as a subscription with a free trial period or a “free” donation when the possible user decides how much it is ready to spend for the access.

Usually, such API type is used for eCommerce or weather broadcast apps, third-party login, etc.


Summing up all the above, we may conclude, that the corporate distribution type is a kind of combination of private and public ones, “the golden mean”. You can use it for free for personal purposes, allowing testing available features. However, full-fledged usage of API by business users like corporations and organizations is paid.

But we can also group the APIs not only by the release policies but, for example, by the systems they are working with, or the options they offer.

By Areas of Work

  • Database APIs. This type of API works directly with databases or database management systems. They are usually used to connect an app with a database to have access to the information needed. It could be used, for example, to enable third-party login on the websites.
  • OS APIs. These APIs allow the creation of an emulator of another OS. For example, Microsoft API for macOS, or enables connection to Microsoft cloud services.
  • Remote APIs. They are used to create connections between different machines and to exchange information between them. It means, that if there is any information needed, it could be delivered via different APIs. Usually, this delivery is done via the Internet, because it is the most common communication method nowadays.
  • Web APIs. This API type is the most popular one. It is used mostly to extend the functionality of the site of the application and to add new features. Such API integration is usually based on the HHTP/s protocols and can be developed even by freelance API developers.

Now we have a slight understanding of API, what it is, and what types of API integration are possible. Nevertheless, there are a few essential rules, every API integration should follow. They are known as API requirements. So what API requirements are and how does API work?

API Requirements

These are necessary conditions that must be satisfied.

It is hard to describe them precisely. Mostly, they are explained superficially, and the exact definitions or the way they are embodied vary. It depends on their purposes or the API protocols, they are based on. That is why API requirements are divided into nonfunctional and functional ones, to describe basic needs in general and to embody them in a particular case, according to the API protocol and the functions it objectifies.

Nonfunctional requirements are descriptive. They just represent the most crucial issues to cope with. Usually, the list of such necessities consists of correctness, performance, reliability, robustness, scalability, security, and usability.

This list could be divided into two different ones: constant and changeable. It is obvious, that correct work, high performance, and reliability, as well as the ability to cope with errors during its work, are essential and must be equally embodied no matter the specifics of the API. On the other hand, such conditions as security, usability, or the number of users that the API could deal with can vary, depending on the goals of the API integration.

For example, the security level of the payment API is much more important and different from the one for advertising API, because the data they operate have a different value. Quite the opposite, advertising API takes care of scalability more, allowing more simultaneous users and visitors.

Functional API requirements are, in fact, the embodied nonfunctional ones, according to the specifics of its type, platform, or API protocols, that are used to develop it. Nowadays, the most common opposition between API protocols is REST API solutions vs SOAP.

What Is The Difference? REST API vs SOAP

It is not exactly the choice between two different protocols. Service Object Acess Protocol is an actual API protocol, while REST is rather a software architectural approach and stands for Representational State Transfer. It was created as an alternative to SOAP. So what is the difference?


It is believed to be one of the first-ever API protocols. It is still used, but its popularity has decreased. The issue is comparing REST vs SOAP, it is easy to conclude that SOAP is much more difficult and “heavy”, and requires hiring dedicated development team.

The main problem is that Service Object Acess Protocol uses an envelope-type structure, which results in long message boards, that accompany every single action to be done. Moreover, such a massive amount of data is harder to analyze. Also, SOAP works only with the XML data format, which limits its possible variations and requires deep knowledge of the protocols and their possible limitations as well.

On the other hand, SOAP is very independent and far more secure than any other alternative. Usually, it is used for financial services or internal purposes such as communication between workers inside the company.


As was said before, REST was created as an alternative way to develop API. It is not a protocol, but an API architectural style. Nowadays, it is the most popular API development approach. REST is easy to deal with thanks to its simple form of communication and basic methods, also known as CRUD operations.

RESTful API uses HTTP protocols, so the user forms the HTTP request and gets an HTTP response from the server. Moreover, such an approach interacts with the data as with the resources, which simplifies the operation processes. This is why CRUD operations are possible to use. There are 4 basic operators needed for the correct work of RESTful API:

  1. POST - allows creating a resource.
  2. GET - allows retrieving the needed resource.
  3. PUT - is used to update or edit the resource.
  4. DELETE - needed to delete the resource.

Despite the fact, that RESTful APIs are easy to develop, they still needed an API descriptive document, as well as any other type of API. What is it and why is it so important?

API Descriptor Documents

API descriptor documents are just documentation for dedicated developers, so they can understand how exactly API works.

Mostly, they exist in the form of manuals with examples and explanations for different cases. API descriptor documents are kind of collections of tutorials and references as well. It is not only about textual description and terminology, but often it presents code-based examples of different acts and actions to simplify the process of understanding the logic of the API structure for dedicated teams or experienced developers for hire.

Also, the documentation may include query and path parameters. These are essentials for the correct work of the whole system.

Path parameters create the linkage with the endpoint, or in other words, make the final product reachable. The main difference between the query and path parameters is the hierarchy. This means that order is very important for the path parameters. It defines the actions to be done and the position of the resources needed.

On the other hand, query parameters enable limitations and specifications of resources required. They help to optimize the search results to narrow down all the possible entries to the list of those, the user is looking for.

There are a lot of different services, which are used to simplify the creation and make it possible to read and visualize the API descriptor documents. For example, PostMan or Swagger.

End Line

So what is API integration? It is an interface that helps to create communication lines between different systems as well as to implement resource-intensive software into your app or website to improve it. API integration has already become a common instrument nowadays.

Despite the main opposition to Restful API vs SOAP, there are a lot of different types of API that are still growing. The main issue with API is that it is almost impossible to conclude or sum up which exact type or style of API is better, every example of integration project is unique and should be considered as an independent system.

The best way to figure it out is to hire dedicated development team or find some freelance developers for hire, who are familiar with such technologies and can explain what exactly you need. Once again, most users and even business owners don't know about such technologies or their advantages.

For instance, you can contact us and our developers for hire will gladly help you with the integration process and explain all the pros and cons of each possible approach. Our dedicated remote software development team has extensive experience in working with all types of third-party APIs, which can be checked in our case studies.

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