Interviewee is expected to demo knowledge and understanding of widely used concepts（ tools Ava) and best practices ( how to use them)

时间分配：

不断重复的小循环

YouTube count example：

• Who will use the system?
  • 观众？ up主？ 其他 AI model （generate recommend）
• How the system will be used?
  • market team use only —> data is not used often
  • sent to recommend system in real time

How fast data is retrieved from the system

• If we need data to count views on the fly —> batch is slow😢

• If we need views count hours later —> batch and stream are both 😊

count while write the data — aggregated data