When a business is growing, a system that was built 20 years ago doesn’t only make modernizing harder, but also stops the platform from scaling.
This was the challenge that our client faced operating Plateau, a B2B platform used by insurance agents across the U.S., with three different applications built on MS Access.
This case is about a phased legacy migration designed to preserve long-standing business logic while gradually moving the product to a modern web stack.
The Starting Point
The legacy applications were still functional, but they were increasingly difficult to evolve.
- The UI was outdated, making it difficult to attract and retain users in a market where modern tooling is expected;
- Three separate applications with no shared foundation meant any cross-system change required three times the effort;
- Existing business rules had accumulated over two decades and could not be lost during migration;
- The codebase had no room for growth and no foundation for integrations, automation, or scale.
Priorities Behind the Build
The project was not a full rewrite. The priority was to move existing functionality step by step while keeping daily operations uninterrupted:
- Migrate legacy functionality to a modern web stack without disrupting ongoing operations
- Preserve the full business logic built into 20 years of legacy code
- Modernize the interface to improve user experience and support growth
- Create a stable, extensible foundation for future product development
Database optimization, DevOps improvements, CI/CD, and broader refactoring were intentionally deferred to keep the team focused on migration continuity.
How We Built It
Team Structure
Across all three applications, the modernization effort involved a team of 20-25 people. Specifically, on the TransCredit application, there were 2 full-stack developers covering both frontend and backend, 2 Business Analysts, 2 QA engineers, and a Project Manager from our Mifort team.
Delivery Process
The team worked in Agile iterations with continuous internal collaboration. The team held daily meetings to synchronize progress, while implementation was driven by an established set of business requirements, with periodic demonstrations provided to the client.
Key Solutions We Delivered
1. Gradual Legacy Migration
Instead of replacing the platform in a single release, we adopted a phased migration approach. New functionality is gradually rebuilt in C# and ASP.NET, and UI modernization was held in Blazor while the legacy MS Access applications continue supporting daily operations until each module is fully migrated.
2. Functional Migration Documentation
Before development began, our BA analyzed the legacy applications, uncovering business rules, dependencies, and workflows that have evolved over more than 20 years. This helped to preserve critical business logic and significantly reduce the risk of losing functionality during the transition.
3. UI Modernization
The outdated desktop interface is being replaced with a modern Blazor-based web interface. This improves usability while allowing the same full-stack team to work across frontend and backend tasks.
4. Grid Customization
Insurance agents work with large volumes of operational data. The team extended standard grid components with custom filters, columns, and fields to better support daily workflows and compensate for UI library limitations.
5. Data Persistence
To avoid disrupting existing business processes, reports remain available in Excel and PDF formats, ensuring users can continue working with familiar outputs throughout the transition. The solution runs on U.S.-based Virtual Machine, meeting the client’s infrastructure requirements.
Results and Impact
- 3 legacy MS Access applications are in active migration to a modern web stack
- TransCredit has reached 15% migration completion
- Legacy and modern systems run in parallel
- A modern, extensible codebase is being established, ready to support integrations, new features, and future infrastructure improvements once the migration phase is complete
Final Thoughts
Legacy modernization is about more than replacing outdated technology. It requires preserving years of business knowledge, reducing migration risks, and ensuring critical operations continue without disruption.
With our practical experience in legacy migration and our ability to work with complex enterprise systems without disrupting operations, we helped our client to move forward, not only by avoiding the business risks, but also helping with future growth.
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