HLD-226·Caching & Consistency
Medium · 1,000 ptsEnterprise Calendar Scheduling, Recurrence & Sync
Design Google Calendar’s core event storage, RRULE recurrence expansion, and attendee calendar synchronization handling top-of-hour reminder bursts.
Max p99
≤ 55 ms
Availability
≥ 99.5%
Budget
≤ $5,550
Functional Requirements
- FR-1POST /calendars/{user_id}/events — Creates single or recurring meetings and fans out attendee invites.
- FR-2GET /calendars/{user_id}/agenda — Fetches expanded daily/weekly event view with read-after-write consistency.
- FR-3PATCH & DELETE /calendars/{user_id}/events/{event_id} — Reschedules or cancels meetings and immediately invalidates attendee agenda caches.
- FR-4Must absorb xx:00/xx:30 meeting-join storms and survive primary DB failover.
Workload Profile
Workday Baseline30,000 Agenda Read RPS / 4,200 Event Write RPS
Top-of-Hour Meeting Rush88,000 Read RPS / 11,000 Write RPS
Active Working Set24 GB active 30-day enterprise agendas
Traffic DistributionSynchronized spikes at :00 and :30 across timezones
Consistency Model
Read-after-write consistency on organizer/attendee agenda views so rescheduled links appear immediately.
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Design Write-up
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