A Norwegian vehicle leasing company manages hundreds of fleet contracts, customer relationships, invoicing runs, and vehicle lifecycles every month. Their entire platform had been running on the same core since 1998 — a Microsoft Access database with VBA forms that nobody fully understood anymore, duct-taped to a homemade C# monolith with NHibernate, WinForms, and MSSQL, running on bare-metal servers on-prem.

The system worked, in the way that a structure held together by years of patches and institutional memory works. Every change was high-risk. Errors were constant. The hosting infrastructure was being kept alive on willpower. The original developers had long since moved on, and the business logic embedded in that Access database existed nowhere else — not in documentation, not in anyone's head with certainty.

Key challenges:

The pressure was clear: keep it running, or replace it. The risk of replacing it, without understanding it first, was the problem.

Before writing a single line of new code, Kodebaze analyzed the entire legacy estate. The Access VBA forms, the C# monolith, the NHibernate data layer, the WinForms UI, the MSSQL stored procedures - all of it was scanned, classified, and mapped.

What emerged was a complete picture of the domain: where the business logic actually lived, what the data structures represented, which modules were tightly coupled and which could be extracted independently, and where the hidden dependencies between the VBA layer and the C# backend were creating the most risk.

That understanding became the foundation for the new architecture — not a guess about what the new system should do, but a verified map of what the old system actually did. The new platform was designed around that map:

A ReactJS + .NET backend on Azure, replacing the WinForms monolith

A dedicated backend API platform handling vehicle catalogue, pricing, and residual value data, replacing the Access/MSSQL pricing logic

Domain-separated services for Customers, Contracts, Vehicles, Invoicing, and Notifications

Replacing bare-metal on-prem with managed cloud hosting, CI/CD pipelines, and Azure Functions for scheduled jobs

Replacing the homemade auth layer with a governed, secure identity platform

The key shift was what the analysis made possible. Without a clear map of the legacy domain, the new system would have been built on assumptions - and assumptions about a 28-year-old codebase are expensive to be wrong about. With the map, the team could design the new architecture around what the business actually needed, not what someone thought it needed.

The transformation delivered:

What had been held together by one engineer's institutional knowledge became a documented, tested, governed platform owned by the whole team.

A Norwegian vehicle leasing company went from a 1998 Access database on bare-metal to a modern microservice platform on Azure in nine months — without stopping their business for a single day.

The riskiest moment in any legacy replacement is the gap between what you think the old system does and what it actually does. That gap is where modernization projects fail - not in the new code, but in the assumptions behind it.

The client's Access database had been accumulating business logic since 1998. Norwegian leasing tax rules. EV exemption thresholds. Residual value calculations. Customer-specific pricing logic. None of it was written down. All of it was in the code.

Kodebaze closed that gap before the first line of new code was written. The analysis turned 28 years of accumulated VBA and C# into a documented, navigable domain model. The migration was built on facts, not assumptions. The cutover was incremental, not a leap of faith.

For this client, that meant a modern platform they own and understand — and a business that can move as fast as its ambitions.