大型迁移，新数据库、新框架、新平台，风险很高，因为它们涉及所有内容，但在完成前没有用户可见的价值。安全的方法是增量和可逆的，永远不要进行大爆炸式切换。你按可验证和可回滚的切片进行迁移。
安全迁移的实施方案
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1. Know WHY — a migration with no clear payoff isn't worth the risk.
2. Migrate INCREMENTALLY — never flip everything at once.
3. Run OLD and NEW in parallel — strangler-fig pattern.
4. Use feature flags / DUAL WRITES to shift traffic gradually.
5. VERIFY continuously — compare old vs. new outputs (shadow traffic).
6. Keep a ROLLBACK path at every step.
7. Clean up the old system only AFTER the new one is proven.
绞杀者无花果树模式
包装旧系统，逐个将功能片段路由到新系统，直到旧系统完全被