System Design SNAKE原则 (以NetFlix为例)

  1. Scenario
  2. Necessary: constrain/hypothesis
    1. Daily active user? Ask! eg. 5,000,000
    2. Predict
      1. User
        1. Average Concurrent Users = daily_active_user * average_online_time / daily_seconds
          = 5,000,000 * (30*60) / (24*60*60)
          = 104,167/s
        2. Peak users = average_concurrent_users * 6 = 625,000/s
      2. Traffic
        1. Video traffic speed = 3mbps
        2. MAX
      3. Memory
        1. Memory per user = 10KB
        2. MAX daily memory = 5,000,000 * 2 * 10 = 100GB
          (T级以内的内存都是可以解的)
      4. Storage
        1. Total movie = 14,000
        2. Movie storage (视频会有不同版本) = total_movie * average_movie_size = 14,000*50GB = 700TB
  3. Application: service/algorithm 模块设计
  4. Kilobit: data 数据设计, 不同数据的存储模型
    1. 比如用户服务可以用mysql, 查询逻辑强
    2. 电影文件就用文件存,不用数据库
  5. Evolve: 和面试官沟通
    1. Step1: Analyze
      1. with
        1. More constrains
        2. New use cases
        3. Deeper, more details
      2. from the views of
        1. Performance
        2. Scalability
        3. Robustness
    2. According to 面试官, 加深某一部分的设计

 

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