What is the strangler fig pattern?

The strangler fig pattern is a migration strategy for incrementally replacing a legacy monolith with microservices without a risky "big bang" rewrite. Inspired by the strangler fig tree that slowly engulfs and replaces its host tree, the approach works by: (1) placing a facade/proxy in front of the monolith, (2) extracting one piece of functionality into a new microservice, (3) routing traffic for that functionality to the new service via the proxy, and (4) repeating until the monolith is completely replaced and can be decommissioned. At every step, the system remains fully functional. This pattern minimizes risk by keeping changes small and incremental and is the recommended approach for legacy modernization at companies like Martin Fowler's clients and major banks.