Modern business requires a range of digital components to communicate effectively when transferring data and delivering critical messages. Application programming interfaces, or APIs, are sets of rules that regulate exactly how certain apps or machines connect. If you work with data at all, you’ll have heard of REST or RESTful, and REST APIs — but what is REST API design? We explain below.

Table of Contents

  1. What is REST API?
  2. REST API Use Cases
  3. REST API Design Basics:
  4. Managing REST API Resources:
  5. How Can Help

What is REST API Design?

You now know that APIs allow different apps, devices, or systems to interact with one another effectively. APIs provide a collection of protocols and functions while defining commons sets of commands to achieve successful communication. The API is the interface that lets you easily obtain the data you need without having to understand how the apps are connecting and communicating. REST API design is the skill set required to create effective REST APIs that provide the right functionality for all users.

REST APIs follow a specific architectural style known as RESTful. REST is an acronym for "Representational State Transfer." REST architecture takes advantage of existing protocols, and when talking about web services, REST uses HyperText Transfer Protocol (HTTP), the standard protocol used across the World Wide Web. This makes RESTful APIs widely accepted and supported, which is why large entities like Google, Facebook, and PayPal all use REST APIs.

REST API Use Cases

REST APIs connect a range of services, sending requests and making calls via URIs to ensure that web services work effectively.

Examples include when your e-shop has a “Pay Now” button that easily connects the user to a financial service like PayPal or Apple Pay. Those annoying Twitter bots? They’re powered by APIs triggering messages when specific content gets posted on Twitter. And travel sites that display the prices from a range of accommodation options are using APIs to connect to the relevant services at all the competing hotel websites, providing a single interface for the user to browse.

REST APIs are ideal for businesses that need to get data from their SaaS or other business apps, as most cloud-based services will have a REST API to connect to. This allows organizations to collate business-critical data from CRMs like Salesforce, social media accounts, and company blogs.

Rest API Design Basics

So, you need a REST API for your data retrieval purposes. But how do you go about designing one? The great news is that you can use any programing language to create your API. All you need to understand is the architectural constraints, which you can split into six basic principles.

1. REST APIs Should Have a Uniform Interface

Whenever an API requests data from a resource, those requests should look exactly the same. You can achieve this by using uniform resource identifiers, which we explain in greater depth in the next section. The resources' access should include any data required by the API and the client.

2. Client and Server Independence

Client-Server decoupling is a term that means the apps at either side of the request chain must function in complete independence from each other. The client needs to know the URI of the required resource and that’s all. There shouldn’t be any further interaction between client and server.

3. Stateless APIs

REST API requests are self-contained. They already include all the information required to process the request, so they don’t require any data to be stored or any other server interaction. Self-contained requests like this are stateless.

4. Cacheable Resources

Where appropriate, cacheability of resources on either the server or client-side should be possible. This improves scalability, speed, and/or performance.

5. Layered API System Architecture

As we’ve touched on, because APIs create a communication interface that hides the interactions beneath them, users don’t get to experience exactly how the services connect. REST APIs send calls and responses through various layers to make the end-user experience smoother.

6. Optional Code on Demand

As well as gathering data from requested resources, designers may include an instruction to have a REST API deliver executable code that can run on demand. An example of this is a deliverable Java applet.

Managing Rest API Resources

“A resource is a conceptual mapping to a set of entities, not the entity that corresponds to the mapping at any particular point in time.” ~ Roy Fielding, 2000

APIs are mechanisms that allow an app or service to access particular resources within other apps or services. URIs, or uniform resource identifiers, define what resources the API should connect to. Just like a URL is the exact web address that takes you to the web page you want to visit, a well-designed URI will help API consumers retrieve the data they require from the apps and services they connect to.

URI design usually follows the following format:

scheme "://" authority "/" path [ "?" query ] [ "#" fragment ]

This should not include trailing forward slashes, which you may sometimes see within web URLs. These will change the syntax and disrupt the unique identity of the resource the API is trying to connect.

A URI may connect to more than a single resource. It may connect to a collection of data classed as a single resource. Resources might have sub-collections within them, so understanding the resources your API needs to connect to is vital to effective REST API design. It’s also important to consider how many API requests a single user might make and if that number will put a strain on the network resources.

For example, a consumer interacting with a blog may be able to leave a comment, "like" the post, share the post on social media, or link it to their own blog. Each of these user requests requires an API request. The app or web service has to determine, perhaps via a JSON property or XML element within the request, what resources each request requires and deal with it appropriately. On the other side, the company copywriter will also use an API to update the blog and post new content or add additional tags. The API must be capable of dealing with the required number of resources and sub-resources without creating lag or latency issues for the end-user.

How Can Help

Combining your business data in one secure destination is desirable if you want to analyze and operationalize that data at scale. Extract, Transform and Load (ETL) tools like help companies create effective data pipelines using services like REST API.’s REST API connector helps you connect to a large number of popular business SaaS and other digital services, including Shopify, HubSpot, and MailChimp. This lets you focus less on detailed REST API design, and more on your business.

Get in touch with today and book a 14-day demo to find out how ETL can support your business data integration needs.