Glossary term
What is WebSocket? Meaning for developers
In System Design
A persistent, two-way connection between browser and server. Example: Chat messages arriving instantly.
Learn it properly · System DesignLesson 33: Real-Time Apps: Polling, WebSockets and SSEHTTP only lets the client ask. For “new message”, “rider is nearby” or an AI answer streaming in, the server has to push. Short polling, long polling, Server-Sent Events and WebSockets compared — and how to scale millions of open connections.In Practical Design Problems
A two-way connection between browser and server, opened with an HTTP upgrade. Use it when the client also sends messages often.
Learn it properly · Practical Design ProblemsLesson 5: Design a Notification System (In-App, Push, Email)Polling, long polling, server-sent events and WebSockets, fan-out with queues, read state, user settings, retries and removing duplicates.In Full-Stack Questions
A long-lived two-way connection between browser and server.
Learn it properly · Full-Stack QuestionsLesson 20: Realtime: WebSockets, SSE and Socket.IOPolling vs SSE vs WebSocket, handshake and heartbeats, Socket.IO rooms and acks, scaling with Redis, auth, backpressure and proxy timeouts.In Networking for Developers
A long-lived two-way connection that starts as an HTTP request and then switches protocol.
Learn it properly · Networking for DevelopersLesson 7: WebSockets, Server-Sent Events and Real-Time NetworkingPolling versus long polling, WebSockets, SSE, scaling real-time connections, and a working example of each.