Prefer listening over reading? Press play and enjoy
When a business-critical platform relies on technology that has been unsupported for decades, the risks to security and compliance are no longer theoretical; they are imminent. Many organisations feel trapped between what they expect is a slow, expensive project of a full manual rebuild and the stagnation of technical debt.
This article explores how Codurance navigated this challenge for a large enterprise, moving them off a legacy VB6 environment within a constrained timeframe. We delve into our AI-accelerated delivery model, showing how a 'human-in-the-loop' approach can turn an 18-month projected modernisation project into a delivery measured in just a few months, all while maintaining total business continuity.
Our client is a large enterprise operating in a highly regulated environment. Its operations depend on a business-critical internal platform used across multiple teams to manage core operational workflows.
This platform was deeply embedded in the organisation but built using Visual Basic 6 (VB6), a legacy technology that is no longer supported. This created increasing operational, security and compliance risks, while also limiting the organisation’s ability to evolve the system.
An audit identified that the core application was built on VB6, which had been unsupported for years. This created a clear need to modernise within a defined timeframe.
The client needed to:
An initial proposal to rebuild the system as a modern web application using React was estimated to take 18+ months, making it unviable commercially and operationally.
Additionally, knowledge of the system was concentrated in a single internal developer, increasing delivery risk and limiting long-term sustainability.
One of the most effective techniques was introducing a quality gate pipeline.
We delivered a full conversion of the legacy application from VB6 to C# .NET WinForms, preserving existing functionality, workflows and user experience.
The scope was intentionally like-for-like, including maintaining existing behaviours and even visual elements where required, to minimise disruption and ensure continuity.
AI played a central role across the entire delivery lifecycle:
Developers acted as “human-in-the-loop”, setting direction, validating outputs, and ensuring quality, rather than manually rewriting the system.
The system was migrated form by form, enabling:
The team worked in two-week sprints, maintaining familiar delivery practices while integrating AI into day-to-day workflows.
To ensure quality despite heavy AI usage, we implemented:
We also developed approaches to handle AI limitations, such as:
We reduced reliance on a single internal expert by:
The project was delivered at approximately half the time of a traditional approach, turning what was previously an 18+ month programme into a delivery measured in months.
The team progressed slightly ahead of plan, with strong indications the project would complete early despite aggressive initial timelines.
AI significantly changed the economics of the project, making a previously unaffordable modernisation initiative viable within the client’s budget constraints.
Because the solution was delivered as a like-for-like conversion:
The move to C# .NET WinForms created a clear pathway toward a future web-based architecture, without the risk and cost of attempting full transformation upfront.
The project established a new delivery model where:
This resulted in significantly accelerated learning and delivery velocity over the course of the project.
The success of the engagement led to:
This was not just a code conversion exercise. The value came from combining:
While the client lacked the internal capacity and time to experiment with these approaches, Codurance brought proven practices and real-world experience to deliver both speed and confidence.
By combining AI-accelerated engineering with pragmatic modernisation, Codurance enabled the client to move off unsupported VB6 technology, reduce risk, and establish a modern foundation—delivering in months what would traditionally take years.
Navigating the transition from legacy systems to modern architecture is often a choice between high-risk overhauls or stagnating with technical debt. However, Codurance provides a third choice. By blending deep modernisation expertise with AI-accelerated delivery and software craftsmanship, we help organisations de-risk their business-critical applications in a fraction of the traditional time
Whether you're facing a looming compliance deadline or looking to reduce the cost of maintaining unsupported technology, we partner with your teams to deliver pragmatic, high-quality solutions that provide immediate value and a clear path for future growth.
If you'd like to find out more, get in touch with us today.
A full rebuild as a web application was estimated to take over 18 months, which was commercially unviable. By performing a like-for-like migration to C# .NET WinForms, we eliminated the risks of unsupported legacy software and met strict audit deadlines in half the time, while providing a modern foundation for future web evolution.
AI was used as a force multiplier for our engineers. It handled the bulk of the code conversion, assisted in complexity analysis for better estimation, and supported test generation. This allowed our developers to act as high-level architects and validators, significantly increasing velocity without sacrificing quality.
We implemented strict "human-in-the-loop" engineering guardrails. This included test-led validation (TDD), structured code reviews, and breaking the migration into small, manageable chunks to prevent AI hallucinations. Our focus remained on software craftsmanship principles to ensure the new codebase was maintainable and robust.
The disruption to the end-users was minimal. Because the project focused on preserving existing workflows and UI elements, users could continue their core operational tasks in a familiar environment. The incremental, form-by-form delivery approach ensured that the system remained stable and validated throughout the entire process.
Natalie Gray is Director of Marketing & Growth at Codurance, a global AI-first software engineering consultancy that supports businesses and their investors to drive value through building and modernising sustainable software and platforms at all stages of the investment lifecycle. With more than 20 years in the tech industry, Natalie believes the power to innovate is accelerated when people are able to try new ideas, fail fast and collaborate. This is why, to her, community is at the heart of her approach to aligning business and technology outcomes. Outside of her commercial role, Natalie runs a number of tech meetups, is an advocate for women in tech and enjoys spending time with her family or protecting her 800 day streak on Duolingo.
Artificial intelligence is reshaping the deal economy faster than most businesses can comfortably absorb. For private equity firms and their..
In part 1 of this series of articles, we explored how Artificial Intelligence (AI) is reshaping both risk and value creation in private equity, and..
Rebuilding Codurance’s Internal Time Sheet System Codurance recently conducted an internal engineering experiment to explore how modern AI coding..
Join our newsletter for expert tips and inspirational case studies
Join our newsletter for expert tips and inspirational case studies
