Problem Statement:
Design a video lifecycle management system. A video may consist of different stages during its life cycle:
- Uploaded to TikTok
- Encoded to multiple formats/resolutions
- Hot
- Cold
The target system should manage video stages (uploaded, encoded, hot, cold) and it can apply multiple actions when the video reaches some stage and some conditions.
这道题考察的是一个“视频生命周期管理”设计题，核心是围绕视频在不同阶段（上传、转码、热、冷）之间的状态流转来建模，并支持在满足某些阶段和条件时触发多个动作。解题时通常需要把视频状态抽象成明确的枚举或状态机，再结合事件 / 规则机制维护条件判断与动作执行；如果题目进一步要求高并发或可扩展性，还要考虑状态变更的幂等性、规则注册与触发顺序等设计细节。
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