Integrating legacy systems into your modern infrastructure

Moumita Mukherjee  |  September 4, 2020


Being part of a large organisation usually means you’ll be working with one or more legacy systems. When these systems were deployed, they were the systems of choice for business productivity and line of business applications. Today, however, these systems can limit a business's agility hampering their ability to respond to market forces and curtailing innovation. As a result, organisations are often looking to replace a legacy system with the latest technology.

But replacement doesn’t necessarily mean improvement.

Compare this scenario with an organisation that has several veteran employees under their wing. Most of the time, businesses rely on their expertise to run essential aspects of their operations due to their experience and technical capability. However, what if they are unable to adjust to modern technologies or processes? Even if it were possible to do so, would it be prudent to replace these experienced employees with younger people with new skill sets? Doing so introduces significant risks and can end up being a very costly affair.

This is the dilemma presented in replacing legacy systems as well. In several cases, legacy systems can hold businesses back from leveraging modern technology and IT infrastructure. However, legacy systems often support critical business or IT processes. So, replacing them entirely with advanced systems can entail several difficulties.

Modernizing Legacy Systems Illustration

How do we fix this problem?

In this blog, we will discuss what legacy systems are, and how they can be integrated with newer, more modern systems so that an organisation can successfully achieve its goals.

What is a legacy system?

A legacy system is based on older technology, old methods, application programs, or computer systems, which are related to, or part of a computer system that has been considered outdated. Despite their old-age, however, these legacy systems continue to be in use and are often running mission-critical applications and processes.

We can consider mainframe-based systems as legacy systems as an example. The term “legacy” signifies it has set the way and set some standards to follow. At the same time, it may imply that the system needs replacement as it is outdated.

Why do businesses keep legacy systems?

  • The system works well for the business, and there is no valid reason to replace it.

  • The system may be monolithic, large, and complex, preventing users from redesigning or replacing it. It may also be costly to repair.

  • Training people with the new system may be costlier than the estimated benefits of replacing the company’s legacy systems.

  • The legacy system may need to be always available for the business’s sake to keep the service up and running. To design a new system with the same feature can require more funding. A few examples of such services include financial accounts handling in banks, computer-based reservation systems, power grids, air traffic control, military defence systems, nuclear power plants, etc.

  • The functionality of the existing legacy system is not well understood. This may be because the initial designers have already left the organisation, and no proper documentation exists.

  • There could be an expectation that the legacy system can easily be replaced if necessary, so the decision to do so is deferred.

  • Replacing legacy systems can be undesirable when it is non-institutional, or it is only applied to individual users for secondary functions.

Drawbacks of keeping a legacy system

  • As new technologies come to market, business behaviours and customer buying habits, may change or evolve rapidly. The legacy system may not be able to support these new behaviours or the processes that they introduce.

  • The cost of maintaining a legacy system can increase over time. As a legacy system ages, the know-how to maintain the system becomes more specialised and, therefore, more costly. Replacing compatible hardware for a legacy system can also be expensive if the new compatible hardware that comes with a warranty can even be sourced.

  • Support from the vendor of the application may no longer be available.

  • Even when an organisation still supports a legacy system, it may become unmanageable to handle the complexity that comes with it. Legacy systems are usually massive monoliths that consist of large codebases that often come with poor documentation. This can add to the maintenance burden, and their complexity becomes a hindrance to new technology. Even small changes can create massive problems. It’s also challenging to find proper resources to work with outdated technology.

While retaining a legacy system may be expensive, we can adapt legacy systems to make them compatible with modern technologies.

What should I do with legacy systems?

Does embarking on a digital transformation initiative mean permanently discarding legacy systems?

According to a Gartner report, 90% of existing legacy applications will still be in use in 2023. Hence, we can expect a parallel initiative towards digital transformation while keeping the usability of legacy systems. Change is constant, especially in the world of tech. With the aggressive use of agile methodologies, existing business models are challenged daily.

How will you deal with the constant pressure of change while keeping your essential legacy systems in place?

First, accept that legacy modernisation is a long-term commitment instead of a burden. You will need to build a lasting foundation for change that can better adapt to technology and customer shifts for the long term and the near future.

The solution to this? APIs.

API Centric Platform Capabilities IllustrationAPIs are capable of exposing the data within legacy systems while maintaining their integrity. Leveraging APIs for this purpose allows secure access as well. All these benefits would improve developers’ productivity, allowing businesses to quickly adapt to modern business needs, as they can adapt to advanced technologies and platforms at a faster rate. Thus, the involvement of APIs becomes a vital component in the modernisation of legacy systems, and, in effect, the operations of a business.

However, this is not the end goal — this is simply a step in the right direction that enables the business to be more flexible and adaptable to continually evolving IT requirements in the long run.

Additionally, organisations that choose to embrace API-led connectivity can expose data from legacy systems in a way that protects the integrity of said systems.

APIs also enable the secure and governed access of data while speeding up developer productivity. In this context, APIs should be made discoverable and reusable to become self-serving tools that the organisation itself can utilise to address the business’ changing needs. This eliminates the need for hiring system specialists, which can become costly.

This approach also allows the organisation to plug in new systems and applications into the entire IT infrastructure, which is now ideal for data, applications, and devices, which are integral to the operation of the business and connected via APIs.

How APIs can integrate your legacy systems

  • With the help of APIs, we can expose several functions of the legacy systems for integrating with other systems. Without APIs, this is almost impossible to perform and may even be highly complex. APIs are one of the most common approaches for extending and modernising legacy systems. APIs come in different shapes and sizes and work efficiently to deliver flexibility and high performance.

  • API-led connectivity is considered as one of the most efficient systematic ways to connect applications and data through purposeful and reusable APIs. Following this approach, you can design and develop APIs for a specific purpose. Additionally, you can unlock the data from systems using system APIs, compose the data into processes through process APIs, or even deliver an experience using experience APIs.

  • Creating an API infrastructure, also known as an application network, can extend the longevity of old legacy systems through APIs, while also allowing new systems to be plugged into the net. It’s as easy as plugging in a printer.

  • From building mobile apps to improving their stakeholders’ experience, organisations would be able to realise their business initiatives and have more informed decisions with API-led connectivity.

  • An organisation that wishes to interact with its legacy systems can easily do so with RESTful APIs. These provide efficient, simple, and lean API utilisation, while also being detached from the traditional client-server model.

  • Using APIs, organisations can easily plug and unplug applications, devices, and data sources into their growing application networks. This means they can compete more effectively while applying innovation at a faster rate. At the same time, it provides the necessary agility layer between the existing IT and new IT.

  • One of the significant benefits of using APIs is giving the consumer ease of access, as they only need to interact solely with APIs to access the data. It creates an abstraction regarding how the underlying legacy system is connected to the data source, hence providing greater agility. APIs help organisations to move away from point-to-point integration while also creating a tight coupling between applications.

Toro Cloud’s Martini can solve issues with your legacy systems

Martini is Toro Cloud’s API-centric Integration Platform as a Service (iPaaS) for digital transformation, and it leverages your legacy systems through the use of APIs.

Martini includes everything you need to consume, publish and manage APIs, integrate cloud-based and on-premise applications, manage data, automate business processes, log transactions, and create reports.

Modernizing Legacy Systems With Martini by TORO Cloud

With endpoints available out of the box for the most common protocols and transports, you'll be building sophisticated integrations between your legacy systems, databases, and cloud-based applications faster than you ever thought possible.


We can say that legacy systems are here to stay. However, instead of considering their longevity, we must consider modernisation strategies by leveraging APIs as well. Adopting the legacy approach and building out an application network with it will not only enable significant benefits to organisations but also solve the immediate challenge of integration.

With data integration and modernising legacy systems, organisations have a real opportunity to add value to customers and create new revenue streams using APIs. This will enable third-party providers to access their products and services. This way, organisations can achieve a balance between strategic needs and operational demands to compete and grow. Adopting an API strategy can extend the life of legacy systems and support digital transformation requirements.

With an API-led approach for legacy modernisation, organisations can adapt to changes while offering new services, products, and experiences to customers in a short time.


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