Strangler fig: modernize without taking the system down
Replacing a critical system all at once is like shutting the plane down to swap the engine. The strangler fig pattern does it differently: it replaces the legacy bit by bit, without ever taking the operation offline.
Where the name comes from
The strangler fig grows around its host tree until it replaces it entirely, never leaving a gap. Applied to software: the new solution grows around the old one and replaces it part by part.
How it works in practice
- Identify one part of the system to extract first.
- Build the new version alongside, routing only that flow to it.
- Repeat, piece by piece, until the legacy is gone.
Why it is safer than rewriting everything
- The operation never stops — each step is small and reversible.
- Risk is diluted, not concentrated in one “big launch”.
- Value appears early, not only at the end of the project.
When to use it
It is the default path when a system is critical and cannot go down but needs to evolve. It is how we approach legacy modernization — and the honest alternative to “rewriting from scratch”.
Modernize without a blackout
We change the engine mid-flight: evolving the legacy without stopping the operation.