Don’t let your legacy applications stop you from joining the API economy

The API Economy

APIs are everywhere. It’s hard to look at any tech site these days without seeing at least a couple of articles about APIs and the API economy. The message is the same everywhere: your competitors are using APIs to expand customer reach, foster innovation or to increase revenue. If your company is not doing the same, you’ll get left behind. We won’t go into the benefits of APIs or the API economy in this blog, there are plenty of other blogs and articles around that have already done that. We’ll assume you’re already on board with the whole idea.


For tech giants like Google, Twitter and Facebook, APIs are a given. They have embraced APIs since their inception and are the API success stories everybody always refers to. Start-ups also have the luxury of being able to start with APIs from the beginning: they can easily adopt an API-first strategy. For others, especially older companies that have an IT landscape that has existed for several decades, it’s not that simple.

They often have many legacy applications that contain functionality and data that cannot easily be exposed as APIs. Cobol programs running on a mainframe for example, are hard to expose as REST APIs. Or maybe the technology allows it, but the company simply doesn’t have the people with the required skills to create those APIs.


There are several solutions to overcome this problem. The first is to replace the legacy application with a new off-the-shelf, API-enabled one. This option can be very cost-effective, under the condition that the amount of required customization work is limited. All too often the customizations get out of hand and the associated costs spiral out of control.

The second option is to write a completely new custom application. Companies can use their in-house developers or hire external developers for this option. As has been painfully experienced by many companies that have tried this solution, it is a very risky, time-consuming and extremely costly solution. Millions of lines of undocumented legacy code that need to be translated are no exception. We’re talking about a project spanning several years here, and the legacy application is often modified or expanded during the development of the new application. Few companies have managed to pull this off, and those that have did so at a tremendous cost!

Fortunately there is a third solution: using an integration platform such as IBM Integration Bus (IIB), legacy backend systems can be accessed using adapters and exposed via standard REST APIs. This software contains adapters for a very wide range of backend applications: from Cobol programs running on a mainframe to ERP systems, to file-based programs and databases or … (insert your legacy systems here). This means that you can keep using your legacy application, even expanding it, and using IIB you can expose all this previously unreachable functionality as REST APIs. IIB runs on a variety of platforms such as Windows, Linux and z/OS (mainframe), meaning you can deploy it right next to your legacy applications.

In most cases you need an extra API layer on top of the APIs exposed by IIB that offer an interface tailored to specific clients’ needs. You can use any programming language you wish for that, such as Java, .NET, node.js, etc. API Management tools like IBM API Connect even allow you to do simple routing, transformation and aggregation tasks in the API Gateway layer. API Connect also offers the possibility to implement APIs using Loopback, a node.js framework.

Many companies have used this strategy to successfully participate in the API economy with APIs exposed from legacy applications. It is a cost-effective, efficient and reliable way to get the most out of your existing IT assets, many of which took years to implement. So don’t worry and don’t let your legacy applications stop you from entering the API economy.

As a plus, this architecture also enables a gradual migration/re-write of your legacy system without impacting these newly integrated systems!

Key take-away

Companies with hard-to-expose legacy applications can use an integration platform to expose their valuable assets as REST APIs. Complimented with an API Management platform, they have everything technically required to participate in the API economy and thereby expand customer reach, increase revenue and foster innovation.

Get in touch with us so we can help you get started!