Mobile System Design Mock Interview: Chat App (like WhatsApp)

[@itsanujgarg]

The feedback part was the highlight. Very insightful

[@Humanusphagist]

Thank you Alex & Eugene for this learning experience.

[@codelite700]

I love how in the database section, Eugene is only commenting the table attributes and not actually deleting them.

[@6957-c5k]

Well done guys for this Mock interview. Helped me alot

[@gswift1]

WebSockets communicate over TCP. They allow bidirectional communication but if the communication ends, you have to restart it. There’s no automatic reconnection. There are also a lot of handshake for every connection you open. That can be a con.

[@SamRamezanli]

hey Alex, what is the response to the question you ask at minute 31:26 , "how would you store chat messages in database when you have hundreds of thousands of messages?". I think one way is to have LRU cache concept where we only keep certain number of chats and up to certain number in the database and when a new one is added, we delete the oldest chat. Is this a good approach?

[@cosodelcosito]

More or less, you want to keep the most recent ones handy, but user may start scrolling up to see history, in that case you keep adding messages to the list.. however if you have a cache size too small you will remove the newest messages while the user is scrolling.. so yes have a soft limit, but be flexible when those messages are being consumed by the user.

[@vandanakumari-bm9de]

Was unable to understand the Web socket questions. The voice was not audible

[@codelite700]

@alementuev I thing I'm unable to understand. In the database section Eugene showed schema for Chat Table & Message Table along with their respective attributes, however I think these two relations need to be joined using a foreign key as well. For ex: We need one more attribute called `chat_id` which will be part of Message relation so that once the user open a particular chat, I can retrieve all the messages for that chat from the Message relation.

[@smitycyken500]

Single source of truth 28:00

[@Vivek-b3h8j]

It's too much irritating when someone continuosly saying "uh, umm, yeah etc." and repeating it before every sentence.

[@ПавлоСкляр-д6т]

резко обрывается в конце, ощущение что мордобой обрезали )