shadow-mode
Installation
SKILL.md
Shadow Mode Migration Pattern
Shadow mode mirrors production traffic to a new system without affecting users. The shadow system's responses are discarded — only the production response reaches the user — but both responses are logged and compared to validate correctness.
When to Use This Skill
| Use this skill when... | Use dual-write instead when... |
|---|---|
| Validating read behavior of a replacement service | Both systems need to persist writes |
| Testing performance under real production load | You need the new store to be authoritative |
| Comparing response correctness before cutover | Migrating data stores that must stay in sync |
| Evaluating a new service version safely | The new system needs to receive and store mutations |
| Load testing a new deployment with real traffic | You need strong consistency between systems |