How to Integrate Legacy Systems: Top Challenges and Strategies

Dayana Mayfield


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Integrating legacy systems can be an arduous but necessary task. If you want to use modern, cloud-based platforms, create new user experiences, improve internal processes, and utilize business data, you’ll need to integrate a new solution with your legacy system to make it happen.

The average enterprise uses a starting 1,295 separate cloud-based services. And to be of maximum use, all of these different services should integrate with the legacy system or ERP software.

In this guide, we dive into legacy system integrations, including the benefits, challenges, and steps to get it done.

Benefits of undertaking legacy system integrations

DevSquad Blog How to Integrate Legacy Systems Infographic 1 v1These are the top reasons why companies integrate new applications and services with their legacy systems:

Operational efficiency

The top reason to integrate with a legacy application is to improve operational efficiency. Without that integration, employees might need to manually transfer data, which not only wastes valuable time but also slows down other business processes and introduces data errors.

Utilize existing data

97% of reports in legacy BI systems get completely forgotten and never used again. When you integrate with existing systems instead of ignore them, you have a chance of utilizing existing reports, intelligence, customer data, and more.

Access to modern functionality

Many companies looking to hook up new services to their legacy system are doing so because they’re interested in the new functionality that the service provides. They might be looking for modern BI dashboards that are easy to share with different departments, improved people management tools, or anything else.

Better user experiences

To create modern user experiences, you often need to connect SaaS applications with your legacy system. For example, a local retailer with hundreds of products might need to integrate their old inventory management system with an ecommerce solution like BigCommerce to take their business online.

Faster to implement new solutions

Integrating your system can allow you to implement new technologies faster than if you were to modernize your entire application. And hopefully, you’ll build an API for your legacy application so that any new solutions can be implemented even faster.

Avoidance of full-blown modernization

When you integrate with your legacy system, you can avoid modernizing the entire system. You can rely on third-party tools for new functionality, better efficiency, and improved user experiences—all without having to rebuild your core business system from scratch.

The challenges of integrating legacy systems

DevSquad Blog How to Integrate Legacy Systems Infographic 2 v1Although there are plenty of benefits to an integration project, there are also plenty of landmines. The following issues could all arise—meaning that rebuilding the system with modern frameworks might be the better option.

Lack of necessary skills

Your internal team might lack the necessary skills to integrate with your legacy system. Or, the time that it would take to do could be higher than modernizing the system and then connecting additional products and services.

Lack of documentation

How long ago was your legacy system developed? Does your team still have access to detailed documentation? Has all knowledge been retained and passed down?

Lacking the necessary documentation could spell disaster for your integration project.

Outdated architecture

While many development teams believe monolithic architectures are always doomed, the reality is that it’s just not that simple. Sometimes monolithic architectures are better than micro-services, because they don’t generate unnecessary complexity.

Your data and system architecture would be considered outdated if it’s challenging for developers to maintain and update, and if it’s resulting in clunky code and time-consuming code reviews.

If this sounds familiar, your outdated architecture will make the integration project even more complicated.

Cybersecurity issues

When connecting too different systems, you introduce vulnerabilities. You might not have the right cybersecurity resources to uncover, test, and prevent any new vulnerabilities being introduced.

Project speed

All of these factors can contribute to a slow project speed. If it’s taking so long to integrate your legacy system, you might find that you’re better off modernizing it.

Heads up—sometimes it’s better to rebuild your legacy app

Banks and insurance companies spend 75% of their budgets maintaining legacy systems. You have to ask yourself if it’s worth it to keep paying the costs of legacy system maintenance.

You might be better off completely modernizing your software to save money and speed up future innovation.

Which approach is right for you? Integration or modernization (and then integration)? The answer lies in how outdated your legacy system is, how much you’re spending to keep it, to what extent its blocking your progress, and what plans you have for your company in the coming years.

Types of legacy system applications

There are 3 main approaches when it comes to integrating with legacy systems and applications:

1. Service layers

A service layer is added on top of your existing system and it transforms the data from the legacy application before delivering it to the new one. This works in reverse as well, so that data from the new system is transformed in a way that the existing one will accept. This is one of the most common strategies for integrating with old systems.

2. Data access layers

A data access layer (DAL) is not a new service layer, but rather a new database. You can replicate the data in an old system but give it a new data architecture, so it’s easier to transfer and utilize that data in the modern systems you’re integrating with.

3. APIs

An application program interface (API) is an excellent solution because it allows you to more easily integrate with additional services in the future. APIs make aspects of your legacy system readable and available to new services and they provide a ton of flexibility. If you plan on integrating your legacy system with several different services in the coming years, than building a custom API is most likely your best bet.

5 steps for integrating legacy systems

DevSquad Blog How to Integrate Legacy Systems Infographic 3 v1 1For a successful legacy integration project, make sure to follow these steps:

1. Clarify the purpose and requirements of the integration

The first step is discuss and document what the integration will accomplish and get internal agreement. Does the integration need to transfer data in two ways? What database calls are the most essential? How does the data need to be transformed?

2. Assess the legacy system’s capabilities for integration

Next, you need to examine your legacy system. Review its data architecture, code, and UX to determine what’s possible. You might estimate that you can build a custom API in under a month, or you might decide that the integration would be such a challenge, that you have to modernize the system before you integrate it with the new services your company wants to implement.

3. Research potential resources and solutions providers

Do some research to find out if any of the heavy lifting has already been done for you. For example, Shopify’s API and SDK could make it easier for you to bring a retail business into the ecommerce world.

Or, you might find that an integration platform-as-a-service (IPaaS) will be more cost-effective than custom integrations with several different SaaS services.

“What’s needed is an enterprise integration strategy. Importantly, it has to be agile, flexible, and cost efficient. The CIOs that we’re meeting are starting to recognize the need for an integration platform-as-a-service to bring all of these services together to work as a coordinated whole. An IPaaS ensures that you can integrate new SaaS services with the business while avoiding the point-to-point integration nightmare that so often slows the journey to cloud.” – Ben Scowen, Business Lead, Capgemini

4. Choose the type of integration and make it happen

Based on your discovery, it’s time to make your decision about the type of integration work that needs to be done, whether that’s building a custom API, connecting a custom API with an IPaaS, building a data access layer, or a combination.

Make sure you have a product manager to keep all moving parts working in synch.

5. Test the integration and plan for long-term maintenance

The final step is to launch the integration and test it. This includes functional testing, performance testing, penetration testing, and vulnerability scanning.

Make sure you strategize how you will test for quality and security going forward.

You should also update your roadmap with your plans for additional updates or integrations.

Sample project: US Ski and Snowboard team

The US Ski and Snowboard team was experiencing many challenges due to their legacy system, which was challenging to integrate with. They wanted to create a better user experience for young athletes and their families when applying to participate in over 500 ski clubs across the country. The US Ski and Snowboard team also struggled to manage data of their existing Olympic and club athletes. They were also unable to launch an ecommerce store because of the integration challenges.

We built a custom API for their legacy system, and integrated it with a newly built user interface for applications and ecommerce store. This resolved integration issues immediately, while also paving the way for easier integrations in the future.

Read the full case study.

Work with experts in software modernization and integration

When integrating or modernizing your legacy system, you need to work with a fully managed team that puts product strategy first.

Learn more about DevSquad’s unique approach.

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