The big rewrite always fails. The Strangler Fig pattern lets you replace a legacy monolith piece by piece, routing traffic between old and new services, until nothing is left of the original. Here is the proxy layer, the migration workflow, and the data sync patterns that make it work.
Adding "type": "module" to your package.json breaks imports, mocks, and dynamic requires in ways that are hard to predict. This guide walks through the practical migration path: incremental adoption, dual-package patterns, testing compatibility, and the traps that catch every team the first time.