REST API integration: use cases, best practices, and tools

As your organization looks to build integrations, you’ll likely rely on REST APIs, or APIs that conform to the design constraints of the representational state transfer architectural style.

The process of building a REST API integration invites a variety of questions, from the use cases you should prioritize to the best practices you should keep in mind to the implementation tools you should use. 

We’ll address all of these key considerations throughout this article so that you can design, implement, and maintain REST API integrations successfully. But to get us started, let’s align on the definition of REST API integration.

Related: Everything you need to know about the API integration process

What is REST API integration?

It’s the process of connecting applications via their REST APIs. These connections can be built between the applications an organization uses internally or between your product and your clients’ applications.

Related: What is API integration?

REST API integration examples

A few common examples for internal use cases include syncing clients between your CRM and ERP system and sending individuals swag if they sign up for a company event. 

For customer-facing integrations, examples include syncing your product with an HRIS to automatically provision and deprovision users and syncing with a CRM to gain the data needed to fuel your machine learning capabilities (and to help clients log activities in your app to their CRM). 

Let’s taking a closer look at each of these use cases:

Sync clients between your CRM and ERP system

As soon as a sales rep closes an opportunity, finance will want to get notified so that they can begin the process of invoicing them. In addition, the sync should work bidirectionally: If finance struggles to invoice a client successfully, they should be able to notify the designated sales rep without leaving your ERP system.

To help facilitate both use cases, you can integrate your CRM (e.g. Salesforce) with your ERP system (e.g. NetSuite) and build the following:

• A data flow where any time an opportunity is marked as closed in your CRM, it's added to your ERP system (and client's fields are automatically populated in the ERP system based on the corresponding fields in the CRM). 
• Bidirectionally sync that lets sales reps become aware of any issues finance flags (like invoicing) and lets finance keep up with an issue.

Send prospects or clients company swag as soon as they register for an event

To help event registrants feel valued and to grow their affinity with your company, you can integrate the platform you use to manage events (e.g. Eventbrite) with the platform you use to send gifts (e.g. Sendoso) and implement the following workflow: Once someone registers for an event, an alert gets sent to your gift-giving platform with the information the registrant entered. The gift-giving platform can then be set up to automatically deliver a predetermined gift to that registrant. 

Automatically provision and deprovision users in your product

Your clients likely have several new hires and departing employees every week. Forcing them or your team to manually provision each new hire and deprovision each employee that leaves is tedious, unpleasant, and can lead to costly human errors (e.g. failing to deprovision a user who no longer works at the company).

You can streamline any provisioning task by connecting your product with clients’ single source of truth for managing employees—their HRIS. 

Once connected, you can build data flows where any time a client’s employee gets added to the HRIS, they’re also added to your product. Moreover, based on their role, department, and any other variable, you can automatically determine their level of permissions in your app. And, on the flip side, once a client’s employee is marked as terminated in the HRIS, they can be automatically removed from your product.

Add critical client data to fuel your product’s AI and ML features

Imagine you offer a product that uses a machine learning-powered algorithm to provide recommendations to sales reps on the leads they should pursue.

To improve these recommendations over time for clients, you’ll need to gather as many insights as possible from critical data sources—and none is more important than clients’ CRM systems.

With that in mind, you can integrate clients’ CRM systems with your product and pull in critical data, like closed-won opportunities. You can also build syncs from your product to your clients’ CRM systems (as your end-users are more likely to benefit from them directly). For instance, any time an account recommendation gets accepted by a rep in your product, a new opportunity can get created for that account in the client’s CRM.

Related: Common examples of API integration

Best practices for building REST API integrations

Here are some best practices that can help guide your implementation process:

Gain an in-depth understanding of the underlying APIs 

Your team should take the time to comb through each application’s API documentation to understand any nuances with the API endpoints you’re looking to build to. This includes areas like rate limits, pagination, and authentication. Any oversights in understanding these core components of an API can compromise the integration’s performance over time.

Design error-handling processes

Unfortunately, API integration issues can crop up for a number of reasons, whether it’s due to an API outage, a bad API key, missing permissions, etc. 

If you can build a workflow internally that alerts the appropriate stakeholders in the applications they rely on for tracking incidents (e.g. Splunk), the integration issue can have minimal impact on your business and your clients. Even better, you can invest in an API integration tool that can notify the appropriate stakeholders and help them troubleshoot any issue, fast.

Test your API integrations rigorously

Before pushing any integration live, you’ll want to test it in a staging environment that closely resembles your production environment. That way, you’re more likely to pinpoint and address the most relevant issues. Similarly, you’ll want to use data that’s similar to what would be leveraged in production in order to make the tests as realistic as possible.

In addition, you should perform tests that would yield successful responses and unsuccessful ones to see how it handles each scenario.

REST API integration tools

The integration tools you’ll consider will vary depending on whether you’re looking to build integrations in-house or with your product. 

Let’s review the tools you might consider for each scenario.

Related: Best practices for performing API integration testing

Tools for internal integrations

You’ll likely find yourself choosing between two sets of tools: robotic process automation (RPA) software, which uses scripts, or “bots”, to automate UI-based tasks; and an integration platform as a service (iPaaS), which lets you build integrations and develop data flows that work across the connected systems.

An RPA solution is ideal when you’re looking to connect data from applications that don’t offer APIs; it also works well when the UIs of the applications you need to integrate don’t change frequently and the volume of data that needs to be synced stays relatively low over time.

That said, RPA solutions are often fairly brittle. A simple UI change in an application can, for instance, break the RPA bot. In addition, as you look to automate more tasks, you’ll need to implement and monitor more bots, which can prove difficult if you don’t have the technical resources available to support this effort.

An iPaaS, on the other hand, is more resilient and better suited to sync data quickly. However, similar to RPA, the platform can only be used by technical personnel, like engineers, which makes it difficult to scale your integrations.

Tools for customer-facing integrations

As you look to build product integrations, you’ll likely find yourself choosing between unified APIs, embedded iPaaS solutions, or an integration marketplace as a service (iMaaS).

• An embedded iPaaS lets you embed an iPaaS solution into your product in several ways. For example, you can embed the iPaaS solution with the product’s UX or you can embed it with your company’s branding. In addition, your team can deliver the integrations on the client’s behalf and/or you can allow clients to build them.

• An iMaaS enables you to design and embed an integration marketplace into your application through an iFrame. Once embedded, prospects and clients can easily find the integrations you provide and go on to build them.

• A unified API solution offers a single, aggregated API that lets you access multiple integrations in a given software category.

An embedded iPaaS and iMaaS both provide pre-built connectors, but these connectors often fall short of your connectivity requirements. Moreover, both platforms require you to build one integration at a time and they require technical expertise to use (your engineers will likely have to get involved). Taken together, the platforms will make it difficult for your team to integrate at scale, quickly.

A unified API solution neatly addresses this by only having you build to a single, aggregated API. In addition, with Merge, the leading unified API platform, you’ll be able to access hundreds of integrations across key software categories, such as ATS, HRIS, file storage, and CRM. You’ll also be able to enable your support or customer success team with monitoring and troubleshooting integrations quickly and easily in partnership with clients; and you’ll gain access to a comprehensive set of common models across our universal APIs, all but ensuring that your clients can access and sync the data they care about. 

Learn more about Merge by scheduling a demo with one of our integration experts.

REST API integration FAQ

In case you have any more questions on REST API integrations, we’ve addressed several more below.

What are the steps to connect to a REST API?

At a high level, here are some steps you’ll need to take:

1. Research the integration requirements via the API provider’s documentation. 

This allows you to identify the relevant endpoint and parameters you should include; understand the authentication method you’ll need to use and how to apply it; pinpoint the provider’s rate limits and pagination method so that you can implement the appropriate logic in your requests, and so on.

2. Test the connection through the API provider’s sandbox account. 

Using this account, you can see if your requests are implemented successfully, your error handling is working as expected, and more—all before any real-world data is impacted. 

You can also perform specific tests like load testing (to see how the integration handles a high volume of requests) and scale testing (to see how the integration performs when managing significant volumes of data) to ensure that the integration can handle edge cases appropriately.

3. Closely monitor the integration once it’s pushed to production.

Even after you’ve tested an integration rigorously, you can still run into unforeseen problems once it’s live. This is especially true at the beginning, as a variety of unforeseen edge cases may not have been addressed.

With this in mind, you should allocate enough developer resources towards monitoring the health of a given integration and troubleshooting any issue successfully.

What are the benefits of integrating REST APIs?

The benefits vary depending on whether you’re implementing internal or customer-facing integrations.

Internal integrations allow your employees to avoid re-entering data across applications, which leads to time savings, fewer human errors, and an improved employee experience.

In the case of customer-facing integrations, your product will become stickier and—all else equal—a better investment. This should translate to higher customer retention, an improved close rate, and an easier time expanding to your target markets. 

What are the challenges of integrating REST APIs?

Common challenges include difficulty in accessing and reading API documentation, lack of resources for maintaining integrations over the course of their lifespans, issues related to securing the API providers’ sandbox environments, and building frequent syncs.