WebSocket for real-time communication in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a WebSocket?

A WebSocket is a communication protocol that provides full-duplex communication channels over a single TCP connection, allowing real-time data exchange between a client and a server.

beginner

How does WebSocket differ from HTTP in communication?

Unlike HTTP which is request-response based, WebSocket allows continuous two-way communication without repeatedly opening new connections, making it efficient for real-time data transfer.

intermediate

What is the role of the WebSocket handshake?

The WebSocket handshake upgrades an HTTP connection to a WebSocket connection by exchanging special headers, establishing a persistent, full-duplex communication channel.

beginner

Name two common use cases for WebSocket in system design.

1. Real-time chat applications where messages are instantly delivered. 2. Live data feeds like stock prices or sports scores that update continuously.

advanced

What are key considerations for scaling WebSocket servers?

Key considerations include managing many concurrent connections, load balancing with sticky sessions or shared state, and handling failover to maintain persistent connections.

What type of communication does WebSocket provide?

A Full-duplex

B Half-duplex

C Simplex

D Broadcast only

WebSocket supports full-duplex communication, meaning data can flow simultaneously in both directions.

Which protocol does WebSocket initially use to establish a connection?

A SMTP

B FTP

C HTTP

D TCP only

WebSocket starts with an HTTP handshake to upgrade the connection to WebSocket.

Why is WebSocket preferred over HTTP for real-time apps?

A Because it allows persistent two-way communication

B Because it supports request-response only

C Because it requires no server

D Because it uses UDP

WebSocket allows persistent two-way communication, unlike HTTP which is request-response based.

Which of these is NOT a typical WebSocket use case?

A Live chat

B File download

C Real-time notifications

D Live sports updates

File downloads typically use HTTP, not WebSocket.

What is a challenge when scaling WebSocket servers?

A Avoiding TCP connections

B Handling stateless connections

C Using short-lived connections

D Managing many persistent connections

WebSocket servers must manage many persistent connections, which is challenging for scaling.

Explain how WebSocket establishes and maintains a real-time connection between client and server.

Think about the initial HTTP step and what happens after.

Describe key design considerations when building a scalable WebSocket-based real-time system.

Focus on connection management and reliability.