dual-write
Installation
SKILL.md
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 compare responses, not persist data |
| Planning zero-downtime data migrations | Mirroring traffic to a staging environment |
| Reviewing code that writes to multiple data stores | Evaluating performance of a replacement system |