Design a Shared Calendar Service
Company: Notion
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
Design a shared calendar service similar to a modern online calendar product. Users can create calendars, create and edit events, invite attendees, accept or decline invitations, view their own agenda, view free or busy availability for other users, configure reminders, create recurring events, and share calendars with different permission levels. Assume the service has tens of millions of daily active users, stores billions of events, and must provide low-latency reads for daily and weekly calendar views. Discuss requirements, APIs, data model, architecture, storage, indexing, consistency, recurring events, reminders, notifications, time zones, scalability, and failure handling.
Quick Answer: This question evaluates a candidate's competency in large-scale system architecture, data modeling, distributed systems, consistency models, event scheduling semantics (recurrence, time zones), and real-time notifications and indexing for low-latency reads.