YOUR BRIEF
What to work through
Work through google Calendar as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- Create, edit and delete events with a time, a place and attendees
- Repeat an event, and change one occurrence or all that follow
- Invite people, who accept or decline and see the event on their own calendar in their own time zone
- See when a group of people is free or busy
- Get a reminder before an event, as a notification or an email
BEFORE YOU START
Constraints to discuss
- About 100 million users, with far more reads than writes (Google report)
- Conflict and free/busy checks answer fast enough to feel interactive
- Times stay right across time zones and daylight saving changes
- A reminder fires on time, and only once
- An organizer’s change reaches every attendee’s calendar
Need a starting point?
Watch for these common gaps as you prepare:
- Writing every occurrence of a series that never ends
- Storing only UTC times, so a 9 AM meeting moves an hour when the clocks change
- A fixed UTC offset instead of an IANA time zone
- Free/busy answers that show event titles to people allowed only busy times
- Scanning every event each minute to find due reminders
- Editing many occurrences one by one instead of splitting the series
Why this question is in the collection
These sources connect the problem to company interview reports or preparation guides. They do not guarantee what a company will ask you.
- Google: PracHub lists a Google onsite report from April 2026: event settings and conflict handling for a calendar like Google Calendar, with repeats, attendees and time zones.
- LinkedIn: A LinkedIn IC2 loop write-up from September 2026, curated by PracHub: round 4 was "Design Google Calendar", on architecture, components and scaling.
- LinkedIn: PracHub lists a LinkedIn onsite report from February 2026: a calendar for users in many time zones, with repeats and daylight saving changes.
- Airbnb: A 1point3acres thread titled "Airbnb Onsite Interview: Designing Google Calendar System", for full-time engineers; its details need a login.
- Uber: PracHub lists an Uber technical screen from May 2026, for a frontend engineer: a calendar like Google Calendar with shared calendars, invites, repeats and free/busy.