Legacy System Modernisation & Reverse Engineering
That old system nobody understands? I map it and rebuild it
Plenty of businesses run on a desktop system built fifteen years ago by someone long gone, with no documentation and a vendor who barely answers. It still holds every rule the business runs on. I take those systems apart, write down what they actually do, and rebuild them properly.
What you end up with
- A written blueprint of a system nobody had documented
- Business rules recovered before the people who remember them retire
- A modern web system your team can use from anywhere
- Freedom from a vendor or a technology that has stopped moving
- Decades of history migrated intact, not abandoned
Signs you need this
If two or three of these sound familiar, it is probably worth a conversation.
- Your core system runs on a desktop machine nobody is allowed to touch
- The vendor barely supports it and the original developer is long gone
- There is no documentation and the people who remember are retiring
- It cannot be reached from outside the office and that now hurts
- You have been quoted a fortune to replace it and cannot judge whether that is fair
What is actually delivered
Not a statement of intent — the concrete artefacts and outcomes you receive.
System archaeology
The existing database, screens and behaviour mapped module by module — what data it holds, what each process does, and which rules are load-bearing.
Requirements blueprint
A written specification of what the system does, in business language, useful to you whoever ends up rebuilding it.
Clean-room rebuild
A new system built from the requirements only — never copied code, screens or schema — so you are not inheriting someone else's legal or technical debt.
Data migration
Years of transactional history cleaned, mapped and moved, with reconciliation reports proving nothing was lost along the way.
Phased cutover
Module by module, running alongside the old system until each piece is proven. No single terrifying switch-over weekend.
How the engagement runs
- 01
Map
Explore the database and the live system to learn what is really there.
- 02
Document
Write the blueprint and confirm every rule with the people who use it daily.
- 03
Rebuild
Build the new system in slices, starting with the foundations everything else needs.
- 04
Migrate
Move data with reconciliation at every step, and prove the totals match.
- 05
Cut over
Switch module by module, with the old system available until nobody needs it.
Legacy Modernisation: common questions
For a substantial ERP, typically several weeks of focused work on the database and the live system, plus interviews with the people who use it daily. It is slower than everyone hopes and it is the foundation everything else depends on.
Yes, and you should. The new system is built module by module alongside the old one, with data flowing between them during the transition. Nobody should be betting the business on a single switch-over weekend.
That is the usual situation, and it does not block the work. The database schema, the running behaviour and the daily users collectively hold the knowledge. Recovering it into a written blueprint is precisely the deliverable.
It is the normal situation, and it is exactly the work. The database, the screens and the people who use it every day hold the answers between them. Recovering that into a written blueprint is usually the single most valuable part of the project — you own your own business logic again, whatever you decide to do next.
It can be, if it is done as a clean-room rebuild: copy the requirements — what each module does and what data it needs — and never the code, schema names, screens or wording. That distinction matters, so I work to it strictly and recommend you confirm the position with your own counsel before shipping.
Yes, and you should. The rebuild runs module by module alongside the existing system, with data flowing between them during the transition. Nobody has to bet the business on one switch-over weekend.
Services that usually go with this
ERP Implementation & Consulting
From selection to go-live, without the six-figure disaster
Business Process Automation
Remove the manual work that quietly eats your margin
Accounting, Reconciliation & Revenue Assurance
Stop losing money you never knew you were losing
Want a straight answer on your situation?
Thirty minutes, no pitch. I'll tell you what I would do and what it costs.