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…