System Design

System design is a wide topic. Even a experienced software engineer at top IT company may not be an expert on system design. Many books, articles, and solve real large scale system design problems may needed.

Steps (S - N - A - K - E)

• Scenario: (Case/Interface)
• Necessary: (Contain/Hypothesis)
• Application: (Services/Algorithms)
• Kilobyte: (Data)
• Evolution

Scenario

Enumerate All possible cases

• Register / Login
• Main Function One
• Main Function Two
• ...

Sort Requirement

Think about requirement and priority

Necessary

• Ask:
  • User Number
  • Active Users
• Predict
  • User
    • Concurrent User:
      • 
    • Peak User:
      • : c is a constant
    • Future Expand:
      • Users growing: max user amount in 3 months
  • Traffic
    • Traffic per user (bps)
    • MAX peak traffic
  • Memory (< 1 TB is acceptable)
    • Memory per user
    • MAX daily memory
  • Storage
    • Type of files (e.g movie, music need to store multiple qualities)
    • Amount of files

Application

• Replay the case, add a service for each request
• Merge the services

Kilobyte

• Append dataset for each request below a service
• Choose storage types

Evolution

• Analyze
  • with
    • Better: constrains
    • Broader: new cases
    • Deeper: details
  • from the views of
    • Performance
    • Scalability
    • Robustness