Three key strategies for legacy system transformation

Legacy software can be dangerous for your business.

It can undermine the security of your data, slow your organisation down, cost money to maintain and harm customer experience and productivity.

Your outdated systems can hold you back – but this doesn’t need to be the case.

We get the frustrations and the challenges behind software transformation projects, but it’s the only way to make the most of the latest updates and upgrades and enhance the user experience.

Once you acknowledge the need to transform your legacy applications, you need to figure out the best strategy to implement this. We’ve done a quick breakdown of the top three…

Iterative modernisation

This strategy involves reviving and adapting an existing application. For this strategy to work, you must be able to visualise a future path for the solution beyond the initial legacy software modernisation.

You’ll start with the initial revamp, getting the solution to a stage where it has a more robust foundation for future development. Then you’ll need the right support and maintenance routine to ensure stability and security of the platform – but what next?

You’ll need to ensure your technical partner can apply future upgrades to the product, adding new functionality to improve user experience or meet organisational needs – all this means you need a codebase with the correct access for iterative development.

Auditing the app is where we start with our clients, implementing a test harness to decipher your product’s behaviour and outputs under varying conditions before changes are made. This will help figure out whether we need to refactor code or upgrade any versions of your legacy product.

We may then replatform the app if we move it to the cloud, iterating upgrades and changes to the app to test their effectiveness and identify any pain points.

Iterative replacement

If your existing codebase or technology stack is too out of date, iterative replacement may be the strategy to pivot towards.

If your app is absolutely critical to your business operations and you cannot function without it, you can develop replacement software, increasing the likelihood that your processes remain intact.
For example, we use iterative development as per Government Digital Service principles to progress through discovery, alpha, beta and live phases.

Our developers define the components that need to be replaced, look at the product strategy and roadmaps, and then determine which components are required for your app’s future use.

With defined components and assessed replacements in place, we assess the app’s architecture to ensure it properly fulfills user needs. At this stage, we can replace components iteratively so that disruption and cost are balanced, moving your users over to the replacement, live software. There may be legacy parts of your software that you no longer need or are no longer being used, in which case we can fully retire these components.

This method can take time to ensure the switchover goes smoothly, and there is a possibility of older and newer systems running in parallel – but if the app is critical to ensure your operational success, it’s important to stick with the roadmap and iteratively replace legacy software.

Waterfall transformation

This would usually be the last resort, as there are inherent risks to effectively switching one piece of software off, and trying to replace all of it in one go.

Usually, this approach would only be adopted if an iterative approach was too costly or time consuming. Urgent governmental policy changes or the expiration of a licence may also be reasons why a ‘big bang’ transformation is required.

How would you achieve this? Start by carrying out a comprehensive discovery and testing phase before implementing this strategy, as well as user research with real data in a pre-production environment.

Through incrementally adding users to your new product, you can mitigate risk and ensure that your organisation’s operations run as smoothly as possible.

What’s our best practice advice?

An iterative approach allows your organisation to assess and analyse your legacy software modernisation project as you go along.


If we were your technical partner for this, our multidisciplinary team would work in close collaboration with your organisation to ensure that your new app is clear and easy to understand, and has the scope to build, adapt and scale, depending on how your organisational objectives mature.


Gone will be the days when data may be undocumented and knowledge is possessed by just a small, select group within your organisation.
6B will transform your legacy applications so that they’re transparent, use modern and open source technology, and support evergreen development for continuous service improvement.

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