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What is Hook0?

Hook0 is an open-source webhook server (Webhooks as a Service - WaaS) that solves the fundamental challenge of reliable event delivery between distributed systems. It acts as a reliable intermediary that receives events from your applications and delivers them to configured webhook endpoints.

The Problem Hook0 Solves​

Modern applications need to communicate with external systems when events occur. Traditional approaches face several challenges:

  • Reliability: What happens when the receiving system is down?
  • Scalability: How do you handle thousands of webhook deliveries?
  • Observability: How do you track and debug failed deliveries?
  • Security: How do you ensure webhook authenticity?

Before vs After Hook0​

Without Hook0​

+-------------------------------------------------------------+
| Your Application                                            |
|                                                             |
| +--------------+    +-------------------------------------+ |
| | Core Business|--->| Webhook Logic (you maintain)        | |
| | Logic        |    |                                     | |
| +--------------+    | - Retry logic & backoff             | |
|                     | - Failure handling                  | |
|                     | - Queue management                  | |
|                     | - Monitoring & logging              | |
|                     | - Security (signatures)             | |
|                     | - Dead letter queues                | |
|                     +------------------+------------------+ |
|                                        |                    |
+----------------------------------------|--------------------+
                                         |
                                         v
                              +------------------+
                              | Customer Webhook |
                              | ❌ Is it down?   |
                              +------------------+

Problems:
  ❌ Webhook code scattered across your application
  ❌ No centralized visibility on delivery status
  ❌ Complex retry/failure logic to maintain
  ❌ Difficult to debug failed deliveries

With Hook0​

+------------------+           +----------------------------------+
| Your Application |           | Hook0                            |
|                  |           |                                  |
| +------------+   |  Simple   | +----------------------------+   |
| | Business   |   |  HTTP     | | Event Processing           |   |
| | Logic      |---|--POST---->| | - Validation               |   |
| |            |   |           | | - Storage                  |   |
| +------------+   |           | +-------------+--------------+   |
|                  |           |               |                  |
+------------------+           |               v                  |
                               | +----------------------------+   |
                               | | Webhook Delivery Engine    |   |
                               | | - Automatic retries        |   |
                               | | - Exponential backoff      |   |
                               | | - Signature generation     |   |
                               | | - Rate limiting            |   |
                               | | - Dead letter queues       |   |
                               | +-------------+--------------+   |
                               |               |                  |
                               |               v                  |
                               | +----------------------------+   |
                               | | Observability Dashboard    |   |
                               | | - All delivery attempts    |   |
                               | | - Failure analytics        |   |
                               | | - Debug tools              |   |
                               | +-------------+--------------+   |
                               +---------------|------------------+
                                               |
                                               v
                                    +------------------+
                                    | Customer Webhook |
                                    | ✅ Reliable      |
                                    +------------------+

Benefits:
  ✅ Single API call to send events
  ✅ Centralized dashboard for all deliveries
  ✅ Production-ready retry logic out of the box
  ✅ Complete visibility and debugging tools

How Hook0 Works​

Hook0 implements a producer-consumer pattern:

  1. Event Ingestion: Your application sends events to Hook0 via REST API
  2. Event Processing: Hook0 validates and stores events
  3. Webhook Delivery: Hook0 delivers events to configured webhook endpoints
  4. Retry Logic: Failed deliveries are automatically retried with exponential backoff
  5. Monitoring: All attempts are logged and can be monitored

Core Concepts​

Organizations​

Organizations are the top-level entity that groups users and applications together. They provide isolation and access control.

Applications​

Applications represent your services or products within an organization. Each application can define event types and have multiple subscriptions.

Event Types​

Event types define the structure and metadata of events your application can emit. Examples:

  • user.account.created
  • payment.transaction.completed
  • order.shipment.shipped

Events​

Events are specific occurrences of an event type, containing:

  • Event type identifier
  • Payload data
  • Metadata
  • Timestamp

Subscriptions​

Subscriptions define where and how webhook notifications should be delivered:

  • Target webhook URL
  • Which event types to receive
  • Authentication headers
  • Retry configuration

Request Attempts​

Hook0 tracks every delivery attempt, including:

  • Response status codes
  • Response bodies
  • Timestamps
  • Retry attempts

Why Choose Hook0?​

Open Source, Self-Hostable or Cloud version​

  • Full control over your infrastructure
  • No vendor lock-in
  • Server Side Public License (SSPL) v1
  • Cloud version available at hook0.com

Built for Scale​

  • Rust-based architecture for performance
  • Horizontal scaling support
  • Efficient retry mechanisms

Developer-Friendly​

  • RESTful API
  • Comprehensive SDKs (Rust, TypeScript)
  • Rich observability features

Production-Ready​

  • Automatic retries with exponential backoff
  • Dead letter queues
  • Rate limiting
  • Security best practices

Use Cases​

SaaS Integration​

Enable customers to receive real-time notifications about events in your platform.

Microservices Communication​

Decouple services by using webhooks for async communication.

Audit & Compliance​

Track all events and their delivery status for compliance requirements.

Third-Party Integrations​

Connect your application to external services like Slack, Discord, or custom systems.

Next Steps​