Comparison
Big bang migrationvsStrangler fig
Big bang migration
everything switched over on one weekend, and the rollback plan was a sentence in a document.
Moving everything from the old system to the new one at a single moment. It is sometimes unavoidable — some data models and some vendors do not allow a gradual path — and it should be recognised as the highest-risk option available, because every problem arrives at once and the rollback window is the same weekend. Where it cannot be avoided, the mitigation is rehearsal: run the cutover against production data more than once before the real one.
Full entry →Strangler fig
you put a router in front and moved one endpoint at a time until the old service had no traffic left.
Replacing a system incrementally by intercepting its traffic and moving one piece of functionality at a time to the new implementation, until the old one can be deleted. Named after the vine that grows around a tree and remains when the tree is gone. It is the default alternative to a rewrite because every step is small, reversible and independently valuable, and because the migration can be paused indefinitely without leaving anything half-built.
Full entry →