The concept

A webhook is the opposite of the API. Instead of your system asking every so often whether there's been a sale, the platform notifies you the instant the event happens, sending the data to an address you registered.

It's what makes delivery immediate: an approved sale triggers access being granted, a refund triggers its removal.

We see our customers as invited guests to a party, and we are the hosts. It is our job every day to make every important aspect of the customer experience a little bit better.

Jeff Bezos Source: Jeff Bezos's letters to Amazon shareholders.

Two rules avoid most problems. Verify the HMAC signature before trusting the notification, and handle re-sends of the same event without duplicating the effect, because the platform repeats the call when it doesn't receive confirmation.

How it shows up in practice

A purchase is approved at your checkout. You need to grant access to the course right away, not hours later after the seller checks email. Instead of your system constantly asking if there was a sale, the platform notifies instantly, sending data to an address you registered.

Implement webhook for immediate delivery. Approved sale triggers access delivery, refund triggers removal. Verify the signature before trusting the notification and handle resends without duplicating effect, because the platform repeats when it does not get confirmation.