The strangler pattern replaces an existing architecture incrementally instead of attempting a risky, all-at-once rewrite. It supports modernization while delivering value in smaller steps. section 12.4.2
A new system initially delegates most work to the legacy system. A routing component directs each request to either the legacy monolith or a modernized subsystem; as more responsibility moves, delegation decreases until the old system is no longer needed or only limited remnants remain. section 12.4.2
Apply the pattern as an evolutionary modernization activity:
- Chunk migration into smaller steps so value arrives sooner and incidents are less severe. section 12.4.2
- Route requests between legacy and modernized subsystems while responsibility shifts progressively. section 12.4.2
- Choose a migration strategy for each subsystem by weighing expected value, investment cost, and return on investment. section 12.6
SoundCloud’s migration
SoundCloud used the strangler fig pattern during an eight-year migration journey, illustrating that gradual replacement can operate across a long-lived modernization effort. section 12.4.2
Use the figure to visualize requests flowing through a router toward legacy or modernized subsystems as responsibility shifts over time. section 12.4.2
