This post is first created by CodingMrWang, 作者 @Zexian Wang ,please keep the original link if you want to repost it.
Requirement
Functional
- Create an event on the calendar
- Send invite to people for the meeting
- Look up all meetings on the calendar
- Send reminder before 30 mins of the meeting
- Cancel the meeting
- Modify the meeting
- Check availability of other members (Out of scope)
Non-Functional
- High availability
- Consistency
- Latency
- Reliability
Estimation
Traffic
- 100M users
- 20M daily active users
- on avg, 2 meetings creation per day -> 40M
- on avg, a user will receive 4 meetings invites -> 80M
- on avg, check calendar twice per day -> 80M
data size
- 100B/user
- 100B/invites
QPS
- 40M/86400 = 500/s
- 80M/86400 = 1000/s
Storage
- user: 100B * 100M = 10GB
- invites: 80 * 365 * 100B = 3000GB
- in total 3TB
Service
- UserAccount Service
- CalendarEvent Service
- Notification Service
API
External
- createMeeting(name, description, startTime, endTime, occuranceFrequency, inviteUsers)
- cancelMeeting(meetingId)
- updateMeeting(meetingId, description, startTime, endTime, occuranceFrequency, inviteUsers)
- checkEvents(userId)
Internal
- sendInvite(meetingId, user)
- createEvent(name, description, startTime, endTime, user)
Data Storage
- Since we have high qps and data size, also we don’t have really complex sql needed, noSql can be a good choice here.
Schema
|Meeting|| |—|—| |id|Hash key| |create user|string| |description|string| |meeting link|string| |occurance frequency|string|
| Event | |
|---|---|
| id | hash key |
| user | global index |
| start time | timestamp |
| end time | timestamp |
| User | |
|---|---|
| id | hash key |
| name | string |
| string |
Diagram
Topics
- How to handle reoccuring meeting
- Create all future meetings ahead / create meetings within a time period, have the scheduler to create future ones.
Workflow
- User create meeting -> calender service create meeting and event for each user, and send messages to message queue, notification send notification to user for invitation.
- Scheduler check db and send 30 min reminder messages to queue.
- User update meeting -> calender service update events and meeting for each user, send messages to message queue for new invitations.
Something more
We can cache user events using Redis for quick calendar check, especially for users who has a lot of events.
