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Webhooks vs Polling vs WebSockets: When to Use What

Webhook Stream ·

Every time one system needs data from another, you face the same fundamental question: who initiates the communication? The answer determines which pattern you use — and choosing wrong means you'll either waste resources, add latency, or build unnecessary complexity.

This post compares the three main approaches — polling, webhooks, and WebSockets — with honest tradeoffs for each. There's no universal winner. The right choice depends on your latency requirements, infrastructure constraints, and how much complexity you're willing to manage.

The Three Patterns at a Glance

Polling: Your system repeatedly asks another system "has anything changed?" at regular intervals. Simple to implement, but wasteful when nothing has changed and slow to detect updates between intervals.

Webhooks: The other system sends your system an HTTP request when something changes. Efficient because you only receive data when there's actually something new. Requires you to run a publicly accessible endpoint.

WebSockets: A persistent two-way connection between systems. Either side can send data at any time with no latency overhead. The most capable option, but also the most complex to operate.

Polling:     Client → Server → Client → Server → Client → Server
             "Anything new?" "No." "Now?" "No." "Now?" "Yes! Here."

Webhooks:    Client ← Server
             (silence until something happens, then server pushes)

WebSockets:  Client ↔ Server
             (persistent connection, either side sends anytime)

Polling

How It Works

Your system sends an HTTP request to an API endpoint on a schedule — every 10 seconds, every minute, every 5 minutes. The response either contains new data or indicates nothing has changed.

// Basic polling loop
async function pollForUpdates() {
  let lastChecked = new Date().toISOString();

  setInterval(async () => {
    const response = await fetch(
      `https://api.example.com/events?since=${lastChecked}`
    );
    const data = await response.json();

    if (data.events.length > 0) {
      await processEvents(data.events);
      lastChecked = data.events.at(-1).timestamp;
    }
  }, 30_000); // every 30 seconds
}

When Polling Makes Sense

You don't control the data source. If you're integrating with a third-party API that doesn't offer webhooks or WebSockets, polling is your only option. Many older APIs and government data sources fall into this category.

Latency doesn't matter. If checking once per minute or once per hour is acceptable, polling is the simplest solution. Batch processing jobs, daily report generation, and data sync tasks often fall here.

You can't expose a public endpoint. Webhooks require a publicly accessible URL. If you're running behind a corporate firewall, on a developer's laptop, or in an environment where inbound traffic isn't possible, polling sidesteps the problem entirely.

The data changes predictably. If you know new data appears at specific intervals (hourly reports, daily summaries), polling aligned to that schedule is efficient and straightforward.

When to Avoid Polling

High-frequency changes with low latency requirements. If data changes multiple times per second and you need sub-second awareness, polling at a reasonable interval will always be behind. Increasing the polling frequency to compensate creates enormous request overhead.

Low change frequency with high volume. If you're polling 10,000 endpoints and only 50 have changes on any given check, 99.5% of your requests are wasted. This is where webhooks dramatically outperform polling.

The Cost of Polling

The math on polling gets ugly quickly. If you poll an API every 30 seconds:

  • 1 integration: 2,880 requests/day — trivial
  • 100 integrations: 288,000 requests/day — noticeable
  • 10,000 integrations: 28.8 million requests/day — expensive

Most of those requests return "no changes." You're paying for compute, bandwidth, and API rate limits to learn that nothing happened.

Webhooks

How It Works

You register a URL with the data source. When an event occurs, the source sends an HTTP POST to your URL with the event data. Your server processes it and returns a 200 to acknowledge receipt.

// Express.js webhook receiver
app.post('/webhooks/payments', (req, res) => {
  const event = req.body;

  // Verify signature (always do this)
  if (!verifySignature(req)) {
    return res.status(401).json({ error: 'Invalid signature' });
  }

  // Process asynchronously — respond fast
  processEventAsync(event);

  res.status(200).json({ received: true });
});

When Webhooks Make Sense

Event-driven architectures. When you need to react to discrete events — a payment completed, a user signed up, a build finished — webhooks are the natural fit. You get notified exactly when something happens, with the relevant data included.

Integrations between backend services. Service A needs to notify Service B when something changes. Webhooks are simpler than maintaining a persistent connection and more efficient than polling.

You need near-real-time updates without the complexity of WebSockets. Webhooks typically deliver within seconds of an event occurring. For most use cases, that's fast enough, and the infrastructure is dramatically simpler than WebSockets.

Multi-tenant platforms. If you're building an API that many customers integrate with, webhooks let each customer receive events at their own URL. This is how Stripe, GitHub, Shopify, and virtually every modern API platform handles event delivery.

When to Avoid Webhooks

The receiver can't expose a public endpoint. Mobile apps, desktop applications, browser clients, and systems behind firewalls can't receive inbound HTTP requests. Webhooks are server-to-server by nature.

You need sub-second bidirectional communication. Webhooks are one-directional (source → receiver) and have HTTP overhead on every event. For chat applications, live collaboration, or gaming, you need WebSockets.

You need guaranteed ordering. Webhooks can arrive out of order due to network timing, retries, and parallel delivery. If strict event ordering is critical, you'll need to implement sequence numbers and reordering logic on the receiver side — or use a different pattern.

The Tradeoffs

Webhooks shift complexity from the sender to the receiver. You need to handle:

  • Endpoint availability. Your server must be up to receive events. Missed webhooks during downtime need to be recovered (usually through a backfill API or replay mechanism).
  • Retry storms. If your endpoint goes down, the sender's retry logic will queue up deliveries. When your server comes back, you may get hit with a burst of retried events.
  • Security. You must verify that incoming webhooks are authentic. Without signature verification, anyone can send fake events to your endpoint.
  • Idempotency. Network issues can cause duplicate deliveries. Your processing logic needs to handle receiving the same event twice.

WebSockets

How It Works

The client opens an HTTP connection and upgrades it to a WebSocket. From that point, both sides can send messages at any time over the persistent connection, with minimal per-message overhead.

// Client side
const ws = new WebSocket('wss://api.example.com/stream');

ws.onopen = () => {
  ws.send(JSON.stringify({ subscribe: ['payments', 'refunds'] }));
};

ws.onmessage = (event) => {
  const data = JSON.parse(event.data);
  handleEvent(data);
};

ws.onclose = () => {
  // Reconnect logic here
  setTimeout(reconnect, 1000);
};

// Server side (using ws library)
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', (ws) => {
  ws.on('message', (message) => {
    const { subscribe } = JSON.parse(message);
    registerSubscriptions(ws, subscribe);
  });

  // Push events as they happen
  eventEmitter.on('payment', (data) => {
    if (ws.readyState === WebSocket.OPEN) {
      ws.send(JSON.stringify(data));
    }
  });
});

When WebSockets Make Sense

Real-time bidirectional communication. Chat applications, multiplayer games, collaborative editing (Google Docs style), and live dashboards all need both client and server to send messages freely. WebSockets are purpose-built for this.

High-frequency updates. Stock tickers, live sports scores, IoT sensor streams — anything where data changes multiple times per second. The persistent connection eliminates the HTTP overhead you'd get with webhooks or polling.

Client-to-server streaming. If the client needs to continuously send data to the server (live audio/video, real-time analytics, typing indicators), WebSockets handle this naturally.

When to Avoid WebSockets

Simple event notification between servers. If Service A just needs to tell Service B "a thing happened" a few times per minute, WebSockets are overkill. Webhooks handle this with far less infrastructure.

You need reliable delivery with retries. WebSocket connections drop. Regularly. Network changes, server restarts, load balancer timeouts, mobile devices switching networks — all cause disconnects. Any message sent while the connection is down is lost unless you build your own acknowledgment and replay system on top. Webhooks with retry logic are inherently more reliable for asynchronous event delivery.

Scale is a concern. Every WebSocket connection is a persistent TCP connection consuming memory and a file descriptor on your server. 10,000 concurrent connections is manageable. 1 million requires significant infrastructure investment in connection management, load balancing (sticky sessions or shared state), and graceful failover. Webhooks scale linearly because each delivery is a stateless HTTP request.

The client is a backend service. If both systems are servers, maintaining persistent connections between them adds operational complexity for little benefit. Webhooks or message queues are simpler and more resilient.

The Tradeoffs

WebSockets give you the most capability but demand the most from your infrastructure:

  • Connection management. You need heartbeat/ping-pong to detect dead connections, automatic reconnection with backoff on the client side, and connection draining during deploys on the server side.
  • State management. Each connection has state (subscriptions, authentication, last-received sequence number). This state needs to survive reconnections, which means storing it server-side and reconciling on reconnect.
  • Load balancing. Standard HTTP load balancers don't handle WebSockets well out of the box. You need sticky sessions or a pub/sub layer (Redis, NATS) so any server instance can push to any client.
  • No built-in delivery guarantees. If a message is sent while the client is disconnected, it's gone. You have to build acknowledgments and replay on top of the base protocol.

Decision Framework

Here's how to choose:

Use Polling When:

  • The data source doesn't support webhooks or WebSockets
  • You're behind a firewall or can't expose public endpoints
  • Update latency of minutes to hours is acceptable
  • You're prototyping and want the simplest possible approach
  • Data changes on a predictable schedule

Use Webhooks When:

  • You need near-real-time event notification (seconds, not milliseconds)
  • The communication is primarily one-directional (source → receiver)
  • Both sides are backend servers with public endpoints
  • You're building a platform that many customers integrate with
  • Reliable delivery matters more than low latency
  • You want the best balance of simplicity, efficiency, and speed

Use WebSockets When:

  • You need true real-time bidirectional communication
  • Updates happen multiple times per second
  • The client is a browser or mobile app that needs live data
  • Latency must be under 100ms consistently
  • You're building chat, collaboration, gaming, or live streaming features

Hybrid Approaches

Many production systems combine patterns. Common combinations:

Webhooks + Polling fallback. Use webhooks as the primary delivery mechanism and provide a "list events" API endpoint so receivers can poll for any events they might have missed during downtime. This is how Stripe and most payment APIs work.

WebSockets + REST API. Use WebSockets for real-time updates in the UI and a REST API for initial data loading and operations. The WebSocket connection pushes incremental changes; the REST API provides the full state.

Webhooks + WebSockets. Use webhooks for server-to-server event delivery (reliable, retryable) and WebSockets for pushing those events to browser clients in real time. The webhook hits your server, your server pushes to connected browsers via WebSocket.

Comparison Table

Factor Polling Webhooks WebSockets
Latency Seconds to minutes Seconds Milliseconds
Direction Client → Server Server → Client Bidirectional
Connection Stateless Stateless Persistent
Delivery guarantee Client controls Retry-based None (must build)
Scale complexity Low Low High
Firewall friendly Yes Receiver needs public URL Needs upgrade support
Resource efficiency Low (wasted requests) High Medium (persistent connections)
Implementation effort Low Medium High
Best for Legacy APIs, batch jobs Event notifications, integrations Live UI, chat, streaming

The Webhook Sweet Spot

For most backend integration use cases — event notifications, data synchronization, workflow triggers — webhooks hit the sweet spot. They're near-real-time without the infrastructure burden of WebSockets, and they're dramatically more efficient than polling.

The challenge with webhooks has always been the operational overhead: building retry logic, signature verification, monitoring, and customer-facing delivery logs. WebhookStream handles all of that, so you get the efficiency and speed of webhooks without having to build the delivery infrastructure yourself.