Web3 · hard

50. Capstone: Building a Web3 Notification Service

Combining queues, webhooks, and events end-to-end.

A production Web3 notification service ties together many concepts: a webhook controller receives and signature-verifies on-chain event payloads from a provider, dispatches a queued job to decode and persist the event, then fires a domain event that triggers user Notifications across mail and database channels. Idempotency keys (based on transaction hash + log index) prevent duplicate processing if the provider retries delivery, and failed jobs are monitored via Horizon with alerting on repeated failures. This architecture cleanly separates ingestion, processing, and delivery concerns, making the system resilient and independently scalable.

Check your understanding

1. Why combine a transaction hash and log index as an idempotency key?
It's required by LaravelTo uniquely identify a specific on-chain event and prevent duplicate processing on retriesTo speed up migrationsTo satisfy CSRF protection
2. What is the benefit of separating webhook ingestion from event processing via a queued job?
No benefit, it adds complexity for nothingIt lets the webhook respond quickly while heavier processing happens asynchronously and can be retried independentlyIt removes the need for signature verificationIt prevents any notifications from being sent