Grokking Webhooks: Stop Polling, Start Pushing Data Like a Pro
This blog demystifies webhooks – a simple way for applications to automatically send messages to each other when certain events occur. You will learn what webhooks are, how they work, and why they’re a game-changer for real-time communication in modern software systems.
You just received a payment on Stripe, and—boom—your app updates the order, sends a thank-you email, and pings your Slack.
No refresh, no waiting, no polling.
Magic?
Not quite.
That’s the power of webhooks.
In this blog, we’ll break down what webhooks are, how they work under the hood, and why they’re a go-to choice for real-time communication between apps.
What are Webhooks?
Imagine you run an online store and use an external payment service (like PayPal or Stripe) to handle transactions.
The moment a customer’s payment goes through, you need to update their order status, send a confirmation email, maybe even notify your shipping team.
How do you find out instantly that the payment succeeded if the payment service is a separate system?
One way is to keep asking the service every few seconds, “Has the customer paid yet? How about now?” – but this constant checking (known as polling) is inefficient and can introduce delays.
Now, what if the payment service could notify your application the instant the payment is completed?
That’s exactly what a webhook does. In plain terms, a webhook is an automatic notification sent from one application to another via an HTTP request when a specific event happens.
It’s like the digital equivalent of a restaurant texting you when your table is ready instead of you standing at the counter asking every minute.
Webhooks let one system push data to another system in real-time, rather than the second system having to pull data repeatedly.
No more waiting around or constant “Are we there yet?” requests – the information comes to you as soon as it’s available.
How Do Webhooks Work?
Webhooks are actually pretty straightforward in how they operate.
Here’s a simple breakdown:
-
Subscription (Registration): First, you (the receiving app) set up a URL on your server – often called a webhook endpoint – and give this URL to the provider application. For example, you tell Stripe, “Whenever a payment succeeds, send the details to
https://myapp.com/payment-webhook.” -
Event Trigger: When the specified event happens on the provider’s side (e.g. a payment success, a new issue opened on GitHub, etc.), the provider prepares an HTTP POST request. This request includes a data payload (usually in JSON) describing what happened.
-
Payload Delivery: The provider’s system calls your webhook URL and sends the HTTP POST with the event data. This is basically the provider saying, “Hey, something just happened – here are the details!”
-
Processing & Response: Your application’s endpoint receives that data. You can then parse it and react to it – update your database, send a notification, trigger some business logic, etc. After processing, your webhook endpoint typically returns a simple response (like an HTTP 200 OK) to acknowledge, “Got it!” to the provider.
This all happens within seconds or less.
For example, if someone opens a pull request on a GitHub repo you’re watching, GitHub’s webhook can immediately POST a JSON payload to your service with details about that pull request.
Your service might then automatically kick off a CI/CD pipeline or post a message to a Slack channel – all thanks to that instant webhook notification.
Think of subscribing to updates.
If you subscribe to a YouTube channel, you get a notification when a new video is uploaded – you don’t have to go check the channel every day.
Similarly, with webhooks, once your app subscribes (provides its URL) to an event, it will get a notification (HTTP request) whenever that event occurs, without constantly checking.
Webhooks vs. Polling (Pull vs. Push)
It’s helpful to understand how webhooks differ from the traditional polling approach (or making repeated API calls).
Here’s a quick webhooks vs polling comparison:
| Aspect | Polling (API Pull) | Webhook (Push) |
|---|---|---|
| Initiation | Client must request data periodically | Server sends data when event occurs |
| Timing | Often delayed (checks every X minutes/seconds) | Real-time – instant on event trigger |
| Efficiency | Can waste resources (many empty checks) | Uses resources only on events (efficient) |
| Setup Complexity | Simple to call an API when needed, but may miss real-time updates | Requires setting up a receiver endpoint, but gets immediate updates |
With polling, your app might ask “any new info?” over and over.
Most of the time the answer is “no new info,” and you’ve spent time and bandwidth on those asks.
Webhooks eliminate that by only communicating when there’s actually something new, making integrations more efficient and responsive.
It’s no surprise webhooks are sometimes called “reverse APIs” – instead of your code calling an API for data, the API calls your code when data is ready.
Tip: Not every service supports webhooks, and sometimes you might still use traditional APIs (for example, to fetch data on demand or if you missed a webhook event). But whenever real-time updates are critical and available, webhooks are usually the better choice.
Conclusion
Webhooks provide a clean, efficient way for systems to talk to each other automatically.
By embracing an event-driven, “don’t call us, we’ll call you” model, they eliminate unnecessary waiting and enable real-time updates across different applications.
For anyone building modern web applications – especially those preparing for engineering interviews or working on system design – understanding webhooks is a must.
It not only helps you integrate services seamlessly but also exposes you to the broader concept of event-driven architecture common in scalable system designs.
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