Every company with a legacy system faces the same dilemma: the old system works (barely), the team depends on it, and nobody wants to be responsible for a migration that goes wrong. So the system stays, accumulating technical debt, security vulnerabilities, and institutional fear.
The Strangler Pattern: Modernize Without Stopping
Instead of a big-bang migration (rip everything out and replace it), we use the strangler pattern: build new modules around the old system, redirect traffic gradually, and retire legacy components one by one. At no point does the business stop.
How the strangler migration works:
- We map every function the legacy system performs and prioritize by risk and business value
- New modules are built with modern tech, wrapping old functionality with clean APIs
- Data flows are redirected gradually: new writes go to the new system, old data is synced
- Each module is validated with real users before the old one is retired
- Historical data is migrated, cleaned, and deduplicated in parallel, not as a big-bang event
We have migrated FoxPro, Access, AS/400, and early-2000s ERPs. The pattern works regardless of how old the system is, because we never ask you to turn it off until the replacement is proven.