Strangler Fig Tree Pattern
The strangler fig tree pattern is a conceptual strategy for replacing legacy systems with new implementations. Instead of replacing the legacy system with a big bang refactor, we incrementally build around the existing system, eventually replacing it in its place.
This is akin to a fig tree in nature, in which the fig tree slowly surrounds another older tree, strangling it, and eventually standing in its place.
Like the strangler fig, our new software slowly but surely strangles the existing legacy software. This is considered a safer pattern for migration off of old legacy systems, in comparison with a big bag all-at-once migration.