Dual Write Migration Pattern Dual write keeps two data stores in sync by writing to both the old and new system on every mutation. This enables gradual migration with rollback safety. When to Use This Skill | Use this skill when... | Use shadow-mode instead when... | |------------------------|--------------------------------| | Migrating between databases or schemas | Validating read-path behavior under real traffic | | Switching storage backends (SQL to NoSQL, etc.) | Testing a new service without writing to it | | Need both systems to stay authoritative during transition | Only need to comp…