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Exploring API Types for Business Success

There are several types of APIs you can use to help your business succeed. Learn about the many different APIs available with this guide.

APIs are crucial pieces of software that enable devices to communicate across networks. You already know that much, but you might not be intimately familiar with every aspect of APIs. If not, then you’re in the right place.

By spending a few minutes learning about APIs and how they work in various circumstances, you can broaden your horizons and ultimately explore new ways to achieve business success.

Below, you’ll find a breakdown of common types of APIs and the architectures behind their designs. With that information, you’ll learn exactly how APIs are helping so many businesses. You'll also be left with the knowledge to help you develop APIs or work on any aspect of your business that can be aided by modern technology.

Primary types of APIs

One of the best ways to get into a discussion about APIs is to highlight the 4 different types of APIs available. Arguably, you could create more than 4 categories, but the vast majority of APIs fall comfortably into the following classifications: open, partner, composite, and internal. These are known as the primary types of API calls.

Whether you're developing APIs for an automated workflow or making pop-up sign-up forms (or anything else involving API communication), you'll find that any of these 4 types are crucial for development.

Let’s look at each in more detail to see what emerges.

Open or public

The term “open” in reference to an API is the same as when it's used to describe any software. Open software is software where the code is made publicly available and free to use or adapt by anyone.

Thus, open (or public) APIs are bits of software that have already been written, and anyone who wants to can use or adapt those APIs as they see fit.

Many APIs are open specifically so that additional apps and tools can easily connect with existing systems. For example, Google maintains a large number of open APIs that make it easy for web developers to build systems that integrate smoothly with Google Chrome.


Partner APIs are designed specifically for communication between business partners. As an example, Apple and AT&T could develop APIs that help iPhones communicate with AT&T's communication infrastructure.

Partner APIs don’t have to be on such a scale. Business partners can develop an API that makes it easy for their systems to communicate with each other. An example of this could be APIs used to automate emails between two organizations.

Additionally, partner APIs can use open or closed software in order to operate, meaning you could have a partner API that's open and free to use.

Partner APIs are often useful for small and medium businesses, just as often as they aid large enterprise organizations. It’s important to remember this. Overlooking this type of API could limit how well you leverage technology for your company.


A composite API combines multiple APIs into a single service. Generally speaking, APIs make frequent requests in order to facilitate communication between devices. Since common devices are complicated and utilize many different APIs, the total sum of communication can require a large number of digital trips back and forth between devices in order to function properly.

Composite APIs specifically look for ways to combine API functions and requests to make communication more efficient.

As an example, composite APIs can organize the communication for email automation triggers. A retail business might have abandoned cart emails that automatically send after an online shopping cart sits un-purchased for a specific amount of time. This system requires multiple communication trips between user devices, servers, and more; thus, the composite APIs are appropriate for consolidating communication resources.

Internal or private

Internal and private APIs are the same thing. These are APIs built around internal logic for a specific business or group. Such APIs are hosted on internal servers (usually) and are developed internally as well.

Private APIs typically serve very specific functions that wouldn’t make sense in another organization. For example, a logistics company might use APIs to facilitate warehouse communication. They may function on customized warehousing API protocols; therefore, they wouldn’t be useful to another business, even in the same industry.

The main point here is that internal APIs are highly customized.

Comparing API architectures

Above, we discussed API types, but there’s more that goes into the discussion. It’s also important to understand the architectures that impact API design. When considering how many APIs there are in the world, knowing about the most common architectures can help set a sense of scale.

Below are the 3 most common API architectures. To be more specific, they aren’t necessarily architectures. In some cases, they're better described as design philosophies or paradigms. Regardless, you'll often develop your APIs according to one of these 3 larger systems.


REST isn't actually a protocol or a standard. Instead, it’s a set of constraints applied to an API architecture. While the complete set of constraints is long and complicated, a few key constraints highlight the gist of REST (also known as RESTful).

  • First, a REST API uses HTTP to communicate across a structure that has clients, servers, and resources.
  • Second, REST doesn’t allow APIs to store information between requests. This is known as “stateless” communication.
  • Third, REST APIs use cacheable data, which helps with client-server efficiency.
  • Finally, REST requires any interface between a system's components to be uniform. There's a whole list of constraints around this specific generalization, but the gist is that all REST interfaces are consistent.

REST is a common API design philosophy because these constraints make development and integration easier and more reliable.


Remote Procedure Call (RPC) is a simplified approach to API interaction. It's used to make Web APIs that can communicate via HTTP or AMQP.

RPC is an older paradigm for API development. As such, it is quite simple, and when that simplicity is sufficient, it makes for fast, easy, and reliable API interactions.

The identifying feature of RPC is that it puts the API method in the URL. The arguments are left in the body. As a result, the client runs the vast majority of API operations.


RPC has been implemented into several architectures, and the most prominent of them is SOAP (simple object access protocol). SOAP APIs are virtually built on top of XML, and this comes with some pros and cons.

On the plus side, SOAP is language-independent, so it works the same across programming languages. It's also transport-independent, platform-independent, and suitable for built-in error handling.

On the downside, SOAP isn't the fastest architecture. SOAP lends toward explicit surface operations, which is good for consistency but slows down intense communication in modern settings.

Benefits of using APIs

Now that you know a few APIs and their architectures, it’s easier to understand how they can benefit your business.

When you develop your own APIs, you can simplify automation tools. You can create software that enables your tools to communicate with each other, and with the use of private APIs, you can customize that software to whatever extent is needed.

With a similar mindset, you can leverage open API development to help your systems integrate with third-party applications. You can even leave the door open to third-party developers to make APIs for tools that work well with your business.

Other benefits of using APIs include data collection, aggregation, and segmentation and improving communication, such as through social media posting.

You have endless options when you learn how to leverage APIs for your business’s goals.

How to choose APIs for your business

It’s an important question. You have these options, so how do you make the right choice?

In most cases, the needs driving API development will affect your final decision. What's the purpose of the API? What's it supposed to accomplish? If it has to function in a highly customized environment, then it will be a private API by necessity. If you need it to be accessible by third-party developers, then you should probably make it open.

Ask yourself the key questions. What do you need from the API? How can you accomplish your goals? Once you can list those answers, you’ll know which direction you should take, and your API development will progress naturally.

Implementing APIs into your business

With a broader look at APIs, their types, and the common architectures, you’re ready to dive in. You can look for some development tools that help you produce better APIs with smaller investments of time and effort.

For those tools, look no further than Mailchimp. Even if your goal is as simple as building your email list and automating transactional messages, Mailchimp is here and ready to help.

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