Every large organization eventually faces the same challenge: systems built for a different era are holding back digital ambitions. The question isn't whether to modernize — it's how.
The Strangler Fig Pattern
The strangler fig pattern, named after a tree that gradually encases and replaces its host, involves building new capabilities alongside the legacy system and gradually migrating functionality until the old system can be decommissioned. This approach minimizes risk — the legacy system continues operating throughout, and the transition can be paused or reversed if problems arise. It's almost always the recommended approach for mission-critical systems.
When Big Bang Makes Sense
Despite its risks, big bang modernization (replacing a legacy system entirely with a new one) sometimes makes sense. When the legacy system is truly an island — minimal integrations, clear boundaries, non-mission-critical — the simplicity of a clean replacement can outweigh the risk. The key is honest assessment: organizations frequently underestimate integration complexity and overestimate their own project execution capability.