REST vs WebSocket

REST and WebSocket serve fundamentally different communication needs. REST follows a request-response model where the client always initiates. WebSocket establishes a persistent, full-duplex connection where both sides can send messages at any time.

When Request-Response Falls Short

REST works perfectly when the client knows when it needs data — fetching a user profile, submitting a form, or querying a search index. But when the server has new information for the client (a new chat message, a stock price change, a game state update), REST forces the client to poll repeatedly.

Polling wastes bandwidth and adds latency. If you poll every 5 seconds, updates are delayed by up to 5 seconds. If you poll every 100ms, you waste 99% of requests when nothing has changed.

WebSocket Architecture

WebSocket starts as an HTTP request with an Upgrade header. Once the handshake completes, the TCP connection is repurposed for bidirectional message passing. Each message has just 2-14 bytes of overhead compared to hundreds of bytes for HTTP headers.

This makes WebSocket ideal for high-frequency, low-latency communication. Learn more about real-time communication patterns in our concept guide.

Scaling Challenges

REST's stateless nature makes it trivially scalable — any server can handle any request. WebSocket connections are stateful, meaning a client is tied to a specific server. Scaling requires sticky sessions or a pub/sub backbone (like Redis or Kafka) to broadcast messages across servers.

The Hybrid Approach

Most production systems use both: REST for CRUD operations and WebSocket for real-time features. For example, Slack uses REST to load channel history and WebSocket for live message delivery.

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The Bottom Line

Use REST as your default for standard API operations. Add WebSocket when you need real-time, server-initiated communication with low latency.