Strangler fig pattern
The strangler fig pattern is a migration approach for legacy systems: instead of replacing the system in one big-bang cutover, incrementally route specific functionality to a new implementation while the old system continues to run. Over time, the new system 'strangles' the old until the legacy is fully replaced.
The name comes from the strangler fig tree that grows around a host tree and eventually replaces it entirely. The pattern was popularised by Martin Fowler around 2004 and remains the dominant approach to legacy migration. The mechanics: put a façade (API gateway, load balancer, ingress) in front of both systems; route specific endpoints, customer segments, or feature flags to the new system; expand the routed surface incrementally as confidence builds; decommission the legacy when nothing routes to it. The trade-offs: longer transition period than big-bang, but radically lower risk — the team can pause, reverse, or adjust at any point.
Discussed in our use-cases
ICP-targeted pages where strangler fig pattern is part of the framing.
Related terms
- Evolutionary architecture
Evolutionary architecture is the design approach that explicitly plans for architectural change over time — building in fitness functions, modular boundaries, and incremental migration paths so the architecture can evolve without big-bang rewrites.
- Modular monolith
A modular monolith is a single deployable application internally organised into well-defined modules with explicit boundaries, typed contracts between modules, and independent ownership.
- Feature flag
A feature flag is a runtime toggle that gates whether a code path is active.