WebSockets vs. Webhooks

Overview

WebSockets provide full-duplex, persistent connections for real-time bidirectional communication between client and server. Webhooks are HTTP callbacks where server notifies client (another server) when events occur.

WebSockets are for client-server real-time updates. Webhooks are for server-to-server event notifications.

Key Concepts

WebSocket

Persistent connection, both client and server can send messages anytime. Like a phone call.

Webhook

Server makes HTTP POST to client-provided URL when event happens. Like a text message.

Long Polling

Alternative to WebSocket. Client keeps HTTP connection open until server has data. Less efficient.

How It Works

WebSocket Flow:

Client sends HTTP upgrade request
Server upgrades to WebSocket protocol
Connection stays open
Both send messages freely
Either side can close

Webhook Flow:

Client registers webhook URL with server
Event happens on server (e.g., payment received)
Server makes HTTP POST to webhook URL
Client's server receives POST, processes event
Client responds with 200 OK

When to use:

WebSocket: Chat apps, live sports scores, collaborative editing
Webhook: Payment notifications, GitHub commits, Stripe events

Use Cases

WebSocket: Chat applications, gaming, stock tickers, collaborative editing

WebSocket: Live notifications, real-time dashboards

Webhook: Payment processing callbacks, CI/CD triggers, third-party integrations

Webhook: GitHub/GitLab events, Stripe/PayPal notifications

Best Practices

WebSocket: Implement heartbeat/ping-pong to detect dead connections

WebSocket: Use sticky sessions or Redis for multi-server setups

WebSocket: Implement reconnection logic on client

Webhook: Validate signatures to verify source

Webhook: Implement idempotency (same webhook can be sent multiple times)

Webhook: Return 200 OK quickly, process asynchronously

Webhook: Implement retry logic on sender side

Interview Tips

What Interviewers Look For

•
Clearly differentiate: WebSocket for client-server real-time, Webhook for server-server notifications
•
Mention alternatives: Server-Sent Events (SSE) for one-way server-to-client
•
Discuss WebSocket scaling challenges: connection state, load balancing
•
Talk about webhook security: signature validation, HTTPS
•
Explain idempotency importance for webhooks
•
Mention WebSocket libraries: Socket.io, ws (Node.js)
•
Discuss when to use polling instead (simpler, but inefficient)