---
title: "Webhooks & Event Notifications — Definition & Engineering Context"
description: "A webhook is an HTTP callback that allows one system to notify another system in real time when a specific event occurs — eliminating the need for polling APIs and enabling event-driven integrations between ERP modules and third-party services."
canonical: https://erpstack.io/glossary/webhook
markdown_url: https://erpstack.io/glossary/webhook.md
publisher: ERPStack
---

# Webhooks & Event Notifications

> **Definition:** A webhook is an HTTP callback that allows one system to notify another system in real time when a specific event occurs — eliminating the need for polling APIs and enabling event-driven integrations between ERP modules and third-party services.

## In depth

Polling APIs (repeatedly checking 'has anything changed?') is wasteful and slow. Webhooks invert the relationship: the source system sends an HTTP POST to a registered URL when an event fires — e.g., Stripe sending a payment.succeeded event to your ERP's billing module. Webhooks require endpoint signature verification (HMAC-SHA256) to prevent spoofed events, idempotency key handling for retries, and dead-letter queues for failed deliveries.

## How ERPStack applies this

We build hardened webhook endpoints in Next.js API routes with Svix or in-house HMAC signature verification, idempotency keys backed by PostgreSQL, and SQS dead-letter queues for zero-loss event delivery.

## Related reading

- [Event-Driven Architecture](https://erpstack.io/glossary/event-driven)
- [Idempotency in API Design](https://erpstack.io/glossary/idempotency)
- [API-First Development](https://erpstack.io/glossary/api-first)