Webhook Processing System

Relevant source files

The following files were used as context for generating this wiki page:

• WEBHOOK_IMPLEMENTATION.md
• lib/webhook-verifier.ts
• app/api/webhooks/stripe-events/route.ts
• PHASE_1_COMPLETION_SUMMARY.md
• PROJECT_COMPLETION.md
• MONEY_TRANSFER_START_HERE.md

The Webhook Processing System in BankChase provides a robust, secure, and asynchronous framework for handling real-time event notifications from external payment providers and internal banking operations. The system is designed to facilitate immediate updates for critical financial activities, such as fund transfers and balance adjustments, while maintaining strict security through cryptographic verification.

This system serves as a bridge between BankChase and third-party services like Stripe, Paystack, and international payment networks (SWIFT, Wise). It ensures that internal ledgers and user balances remain synchronized with external transaction statuses through a reliable delivery and retry mechanism.
Sources: WEBHOOK_IMPLEMENTATION.md:3-10, PHASE_1_COMPLETION_SUMMARY.md:12-19, MONEY_TRANSFER_START_HERE.md:21-25

Architecture and Data Flow

The architecture follows a non-blocking, event-driven pattern where webhook deliveries are initiated asynchronously to prevent latency in core banking flows. The system categorizes webhooks into management (CRUD), event triggering, and background retry processing.

System Components

Component	Description
Webhook Manager	Handles CRUD operations for webhook configurations and event subscriptions.
Signature Verifier	Performs HMAC-SHA256 verification to ensure the integrity and authenticity of incoming payloads.
Event Dispatcher	Asynchronously triggers events (e.g., transfer.completed) and manages initial delivery attempts.
Retry Worker	A background job that processes failed deliveries using exponential backoff logic.

Sources: WEBHOOK_IMPLEMENTATION.md:219-234, PROJECT_COMPLETION.md:16-25, lib/webhook-verifier.ts

Webhook Event Life Cycle

The following diagram illustrates the lifecycle of a webhook event from initiation to successful delivery or final failure after retries.

The diagram shows the asynchronous flow of event triggering, persistent logging, and the retry loop for failed deliveries.
Sources: WEBHOOK_IMPLEMENTATION.md:154-175, PHASE_1_COMPLETION_SUMMARY.md:46-60

Security and Verification

Security is a primary pillar of the webhook system, utilizing industry-standard cryptographic methods to prevent unauthorized data manipulation or spoofing.

HMAC-SHA256 Signature Verification

Every webhook delivery includes a X-Webhook-Signature header. The receiver must compute the HMAC-SHA256 hash of the raw request body using a shared secret and compare it to the header value. This ensures that the payload was not tampered with during transit and originated from the BankChase system.
Sources: WEBHOOK_IMPLEMENTATION.md:135-152, lib/webhook-verifier.ts, app/api/webhooks/stripe-events/route.ts

Encryption and Storage

Webhook secrets are never stored in plaintext. They are encrypted using AES-256-GCM before being persisted in the database, with the encryption key managed through secure environment variables.
Sources: WEBHOOK_IMPLEMENTATION.md:153-156, PROJECT_COMPLETION.md:48-52

Database Schema

The system utilizes three primary tables to manage configurations, audit trails, and delivery attempts.

Webhooks and Events Tables

Table	Field	Type	Description
webhooks	secret	Encrypted String	Shared secret for HMAC signing.
webhooks	events	Array	Subscribed event types (e.g., balance.updated).
webhook_events	status	Enum	Current state: pending, succeeded, failed, max_retries.
webhook_retries	attempt_number	Integer	The current attempt count (1-5).
webhook_retries	response_code	Integer	HTTP status code received from the endpoint.

Sources: WEBHOOK_IMPLEMENTATION.md:14-53, MONEY_TRANSFER_START_HERE.md:45-72

Retry Logic and Reliability

To ensure high availability, the system implements an exponential backoff strategy for failed deliveries. This window extends up to 24 hours to handle temporary receiver downtime.

Backoff Schedule

1. Attempt 1: Immediate upon initial failure.
2. Attempt 2: 5 minutes.
3. Attempt 3: 30 minutes.
4. Attempt 4: 2 hours.
5. Attempt 5: 24 hours.

After the fifth attempt, the event is marked as failed and no further processing occurs.
Sources: WEBHOOK_IMPLEMENTATION.md:158-166, PHASE_1_COMPLETION_SUMMARY.md:126-128

Sequence of Webhook Delivery

The following sequence diagram represents the interaction between the Internal Banking Engine, the Webhook Service, and the External Client Endpoint.

This diagram highlights the non-blocking nature of the engine and the persistence of delivery status.
Sources: WEBHOOK_IMPLEMENTATION.md:189-204, PHASE_1_COMPLETION_SUMMARY.md:46-60

API Reference

Webhook Management Endpoints

Endpoint	Method	Description
/api/webhooks	POST	Creates a new webhook configuration.
/api/webhooks/{id}	PATCH	Updates URL or subscribed event list.
/api/webhooks/{id}/stats	GET	Returns delivery success rates and response times.
/api/webhooks/payment-provider	POST	Entry point for external provider callbacks.

Sources: WEBHOOK_IMPLEMENTATION.md:57-111, PHASE_1_COMPLETION_SUMMARY.md:92-96, MONEY_TRANSFER_START_HERE.md:104-106

Conclusion

The Webhook Processing System is a production-ready module that guarantees ACID-compliant updates through its ledger-integrated architecture. By combining HMAC verification, encrypted storage, and a resilient retry mechanism, it provides the reliability required for high-volume banking operations while ensuring developer extensibility via standard API endpoints and detailed audit logs.
Sources: WEBHOOK_IMPLEMENTATION.md:243-248, PROJECT_COMPLETION.md:124-129, PHASE_1_COMPLETION_SUMMARY.md:173-178