Google Calendar

October 30, 2024 6:15 PM PDT

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This document outlines the system design interview for Google Calendar, focusing on the requirements, high-level design, and deep dive discussions related to the application's architecture and functionality.

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Requirements

• Support for 500 million monthly active users and 100 million monthly active users.
• Real-time refresh of the UI within under 1 minute.
• Average of 2 events per user per day.

High-Level Design

• Data Schema:

  • Unregistered users will not appear in the database.
  • Events should include start_time and end_time.

• Event Handling:

  • getEvents: Handled by the event service.
  • getInvitation: Handled by the invitation service.
  • createEvent:
    • Flow: User -> Event -> Event Database
    • Event triggers invitation and notification services.

Deep Dive

• Event Retrieval:

  • How to implement getEvents?
    • Change the design to accommodate requirements.

• Database Choice:

  • SQL database is preferred due to high consistency requirements.

• Throughput:

  • Reads: 100 million users * 10 reads per day / (24 * 3600 seconds) = 12,000 reads per second.
  • Writes:
    • Events table: 10,000 writes per second.
    • Invitation table: 6,000 updates per second.

• Notification System:

  • Notifications to users can be sent via email and WebSocket.
  • Registration with the WebSocket service involves:
    • User -> Login service -> Assign notification service -> User.
    • User connects to the WebSocket service with domain name, port number, and URL path.

Additional API Considerations

• Need to add more APIs to support the required functionalities.
• Monitor SQL queries per second (QPS) for performance optimization.