Chapters
0:00 Welcome
0:14 Introduction
1:23 Requirements
7:10 APIs & Entities
16:05 High Level Design
29:35 Deep Dive 1 - How Do We Deal With Recurring Events?
41:09 Deep Dive 2 - How to Support Multi-Device In-Sync Quickly?
49:40 Deep Dive 3 - How to Quickly Check Availability?
1:01:07 Final Design & Recap

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YouTube

A comprehensive walkthrough of designing a Google Calendar backend system, covering functional requirements (event management, invitations/RSVP, calendar viewing, availability checking) and non-functional requirements (strong consistency, multi-device sync, scalability, low latency). The design uses a calendar service with RESTful APIs backed by a relational database. Deep dives explore handling recurring events with exceptions using a series-plus-exception model, implementing real-time multi-device sync through push invalidation with delta sync, and optimizing free/busy checks using incremental materialized views with caching to achieve sub-500ms P95 latency.

Design Google Calendar - Backend Step-by-Step Walkthrough