3 approaches to modernising legacy systems

The process of replacing legacy systems can be daunting. There are many areas to consider and decisions to be made when executing this project. For one, it is important to plan the undertaking so that downtime is minimised and improvements can be made without destroying data. 

Businesses also need to understand the general scale and complexity of an upgrade project. All of this while trying to minimise cost and the risk of failure.

A modernisation project, however, does not require a huge change to your technology infrastructure that disrupts your business. Technology should be viewed as a continuous, measured improvement rather than a one-time event. As part of planning your legacy upgrade, businesses must consider how exactly their legacy systems will be modernised. 

Businesses looking to modernise their existing legacy systems are faced with a variety of approaches. From completely replacing their systems to rehosting their existing data on a new platform. Which approach is appropriate will differ according to the needs and requirements of each business. 

The following article will look at three popular approaches that businesses can take to successfully modernise these existing legacy systems. 

1. Rehost

The process of rehosting your applications involves migrating them to a more modern infrastructure without modifying their code or changing their business logic.

In these scenarios, legacy technology will usually be shifted to a modern app environment. This approach is the least invasive method for modernising your legacy systems. 

Examples of this approach include: 

  • Migrating an application from one cloud environment to AWS
  • Data migration from an on-premise server to the cloud 
  • Upgrading an older Amazon Elastic Compute Cloud (EC2) instance.   

As these examples show, the complexity of rehosting your legacy systems can vary. Hosting your old application in a newer environment is generally less complex than migrating your data from an on-premise server. 

As a whole, rehosting remains a relatively low-risk approach for businesses who are looking to modernise their legacy systems. 

Rehosting your legacy systems means that businesses access the benefits of modern technologies like the cloud without making major changes to application code. A modern hosting solution also solves the issue of expensive maintenance by replacing legacy technology. 

In the case of on-premise servers, for instance, there is a need for an air-conditioned server room as well as staff costs for the administrative work which, in turn, includes patching and virus scanning of the operating system.

This approach is advised if your legacy applications are working to an adequate standard, but the infrastructure behind them is outdated. Legacy infrastructure can lead to problems with regard to costs and security. 

For example, older systems are more likely to be infected with malware. Patching these systems constantly is a frustrating expense for businesses, made even worse in those cases where no patches are available. 

A rehosting approach is more often used as a temporary approach while a new application is being developed. In other cases it can be the first step in a larger rebuild process. 

Whatever the reasoning behind rehosting legacy systems, businesses will benefit from working with a software development partner who can assess your current system set up and plan for any risks that might arise during the modernisation process.

2. Refactor

A refactoring approach involves changing parts of a legacy system to optimise code. Refactoring is a more affordable way to get access to modern technology features without making significant changes to a legacy system.   

This process involves changes on the backend, such as reducing redundancies or errors,  without significantly altering the UI or functionality. The external behaviour of the application will, therefore, remain relatively unchanged. Refactoring is less invasive than rewriting, where developers would create new code and implement completely new functionality.

Here are some scenarios where refactoring might be appropriate: 

  • You want to make improvements to your system but the existing infrastructure makes it very difficult to execute. 
  • You don’t want to change the functionality of your existing system
  • You need to bring a codebase up to a supported version of a framework (e.g. .NET) 
  • Software is becoming increasingly complex and hard to test

The benefits of refactoring are numerous. These include improving stability, scalability and making code more secure and easier to maintain.

A key benefit of this approach is that it is less invasive than a complete rebuild or rewrite approach. Refactoring allows businesses to do a lot with a little. By making some changes to the source code, businesses can begin to make improvements that wouldn’t otherwise be possible. 

These outcomes can usually be achieved without major downtime. This benefit means that businesses can modernise their legacy systems without a significant impact on their operations. 

However, businesses should be aware that technology limitations can limit the possibilities of what can be achieved in the project. The refactoring process does not alter your application’s functionality. For this reason, you cannot make big (and perhaps useful) changes like adding new features.

It is also advised that you do not carry out refactoring without a fairly comprehensive regression test. These tests will verify if the code change brings with it any issues into the existing functionality. Automated tests are a huge benefit here because, once created, automated tests can be repeatedly run to detect any defects. 

As always, the decision to refactor should be preceded by thorough planning of existing processes and systems. Identifying other options, like rewriting or rehosting, and deciding why these are not appropriate. 

3. Rebuild

The most extensive approach to modernising your legacy systems is to completely rebuild them. The purpose of this process is to develop a modernised, cloud-native environment in place of the existing legacy system.

A rebuild approach is a big commitment. Like any software project, a rebuild requires buy-in from stakeholders, as well as an assessment of business requirements. However, a rebuild approach requires companies to more deeply examine the way that they work and be open to adopting new processes. 

Typically, this approach involves completely rewriting the application components and the technology stack. Using new coding languages and techniques, businesses can reduce development time, improve security, and create new standards for data handling.  

New functionalities will, additionally, enable businesses to improve their operations and offer better services to customers. 

Scenarios when a rebuild approach might be used are: 

  • It is too expensive to licence and maintain your existing tech 
  • Your system is no longer fit for its intended purpose
  • The underlying technology for your system is obsolete

One of the main challenges with a rebuild approach is balancing significant change with existing requirements.

Having an experienced software development partner will help you maintain this balance. This partner will be able to scope out the exact requirements for a new system and help modernise your operations. 

Rebuilding, as its name suggests, gives businesses the chance to rethink the technical requirements of their existing systems. With a full rebuild, you are able to tailor the system to your new requirements, implement solid improvements, and reap all the benefits associated with bespoke software development. 

Businesses can leverage new methods and technologies to ensure that their systems are future-proof and scalable. As an example, DevOps emphasises the use of standard processes throughout a business. By standardising processes and procedures, a business is able to smoothly implement a new system while maintaining strong security. 

New systems can also be made flexible and more performant by adopting technologies such as microservices, containers, and serverless functions. In a microservices architecture, for example, each unit of a system is scalable independently. This application architecture enables businesses to scale seamlessly.

Rebuilding your legacy systems offers a wealth of opportunities. The main benefit is that it allows businesses to create a fit-for-purpose system that is scalable, secure and future-proof.  In an ideal world, all businesses would perhaps choose to rebuild their legacy systems. 

Some businesses may also not necessarily need to overhaul their legacy systems as extensively as they think. It might be worthwhile to only invest in modernising the parts that will bring the most value to your business. 

In any case, a software development partner will be able to assess the existing state of your systems. From here, they will be able to provide expert advice on the best approach. The latest technology should be implemented based on business needs, first and foremost. Working with a software development company will allow you to identify which software solutions will improve your business processes.

Finding the Right Approach 

In order to modernise legacy systems, all levels of a business must be involved. Furthermore, these projects require navigating people, processes, and data related to legacy systems. 

Juggling these extra factors can be challenging without the support of a software development partner. This partner will be able to assess existing processes and provide the most appropriate solutions for your business. 

Audacia has extensive experience delivering complex, large-scale software projects for leading organisations — covering legacy system modernisation, migration and integration. Drawing on our years of experience dealing with leading organisations, we can advise you on the best approaches to legacy modernisation. Audacia is also a Microsoft Gold Partner, experienced in analysis and consulting for large complex software projects. 

Interested in finding out more about how you can upgrade your legacy systems? Get in touch with Audacia today on 0113 543 1300, or email [email protected]


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