The Hidden Trap in Backend Tutorials: Why Your Webhooks Are Creating Duplicate Data (And How to Fix It)

Short summary

Webhook handlers must implement idempotency to prevent duplicate data processing when external services retry failed requests. The pattern: store a unique event ID, check if already processed, and return success gracefully for retries. This tutorial provides a complete Node.js/Express code example to eliminate duplicate transactions and maintain data integrity.

• •Networks are unreliable; external services retry webhooks when they don't receive confirmation
• •Idempotency ensures duplicate requests have the same effect as a single request
• •Implementation: check for unique event ID before processing, ignore retries gracefully

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