Building Resilient Webhook Systems

Webhooks are the backbone of modern event-driven architectures. But building a system that reliably processes millions of webhook events is harder than it looks.

Core Patterns

Idempotency

Every webhook handler must be idempotent. Use a unique event ID to deduplicate:

event_id → check cache → if processed, return 200 → if not, process

Retry with Backoff

Networks fail. Services go down. Implement exponential backoff for webhook delivery retries.

Dead-Letter Queue

When all retries are exhausted, route the failed event to a dead-letter queue for manual inspection.

Architecture

Stripe → Cloudflare Workers → Queue → Processor → Database
                                         ↓
                                  Dead-Letter Queue

Monitoring

Track these metrics for every webhook system:

• Delivery rate (events delivered / events sent)
• Processing time (p50, p95, p99)
• Error rate by error type
• DLQ depth