Multi-user Chat

Topic: Multi-user Chat

Interviewer: ken

Level: L5 (Senior)

Additional Resources:

• Live Stream

System Design Interview - Design Uber

9/11/2024

YouTube for the event:

Coach Ken LinkedIn:

https://commitway.com/linkedin

WeChat QRCodes

| | | 职场提升俱乐部 |

Multi-user chat system

[41]

Send and receive messages

Group management

[39]

[38]

[21 TB?]

[35]

Pubsub,

Long polling - wait 5 seconds, poll, and backout

Web socket

Web socket - is better and faster. Reduce handshake. Live conversation. Reduce the round trip.

[33]

Device service

Group manager

Message service is stateful

63k connections per server

Use a hash of user ID, by 10

[ in-house device service. ]

[ Use Or zookeeper ]

[30]

How to discover the message service

App -> device service

App -> message service

[26]

Not sure how to manage web socket

Remove device service

Supporting group

1-1 chat

[can we not use 3rd party?]

First connect to device service

Device connects to a message service

[14:38]

Message will contain sender ID and receiver ID

Message service finds receiver’s message service

Add message queue

Kinesis

Topic = same topic for

One reader per shard

[6]

[3]

Use receiver ID as the sharding key

For each shard we have one consumer

[2]

Does the number of shards need to be the same as message service

Yes

No shard number limit

===

Interviewee self review:

Not clear about websocket

Can manage using zookeeper

How to make a stateless system