Every legacy system reaches a point where change is slow, risky, and expensive. The instinct is to rebuild it clean. The data on big-bang rewrites is not kind — there is a safer path.
Why the big-bang rewrite usually fails
A full rewrite freezes the old system's roadmap for months or years while the new one catches up to features the business already depends on. It underestimates the undocumented behaviour — the edge cases the old code handles that nobody remembers — and it delivers zero value until the very end, when it either works or does not.
Meanwhile competitors keep shipping.
The strangler pattern, in practice
Modernise around the edges. Put a facade in front of the legacy system, then move one capability at a time behind it — a new service for one workflow, the old system for everything else — until the old core is doing less and less. Each step ships value and can be reverted on its own.
This needs an integration layer and disciplined boundaries, which is exactly the first workstream in a Rekoodu enterprise engagement.
Sequence by risk and value
Start with the pieces that are both painful and well-understood — high change frequency, clear behaviour. Leave the mysterious, rarely-touched core for last, by which point it is small and surrounded. Modernisation becomes a series of controlled, reversible moves instead of one irreversible bet.