Versions Compared

Version Old Version 7 New Version 8
Changes made by

thierry sinassamy

thierry sinassamy

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.
Tip

The Framework proposed in this space (Alex Xu) is applied to propose a design : Getting started - a framework to propose...

Introduction

A chat performs different functions for different people. It is important to explore the feature requirements.

Step 1 - Understand the problem and establish design scope

Kind of chat ? 1 to 1 or group chat ?

both

Mobile or Web app ? or both ?

both

Scale of the app ? start-up or massive scale ?

massive scale : 50 millions per day of active users.

Limit for a group chat ?

Max 100 people = small group.

Features ? Support attachment ?

1 on 1 chat, group chat, online indicator, ONLY supports textes messages.

Limit of text message ?

Less than 100 000 characters long.

End-to-end encryption required ?

Not required for now, but maybe.

Chat history ?

Forever

Push notifications ?

Yes.

Multiple device support ?

Yes, can be logged in multiple accounts at the same time.

On this page.

Table of Contents

Step 2 - High-level design

For a chat service, the choice of the network protocols is important : HTTP connection could be a good option on the server-side, but the problem occurs on the client-side. There are 3 techniques to simulate a server-initiated connection: polling, long polling and WebSockets.

See polling & long polling in the page References & Glossary for chat system.

WebSockets is the most common solution for sending asynchronous updates from server to client. WebSockets (WS) is used for both sender and receiver sides.

Image Added

Step 3 - Design deep dive

Step 4 - Pros & Cons