The Silent Killer: Why Webhook Idempotency Matters
You deploy a webhook handler that charges a customer $50 on every payment.completed event. The payment provider retries the webhook once due to a temporary network timeout. Your handler processes it twice. Now your customer is charged $100, and you're fielding an angry support ticket.
This is the core problem with webhook idempotency: duplicate events are inevitable. Network failures, timeouts, provider retries, and even your own restarts can cause the same event to be delivered multiple times. Without webhook idempotency duplicate events handling, you risk corrupting data, double-charging users, or creating orphaned records. The solution isn't to prevent duplicates—it's to make your handler idempotent, so processing the same event twice produces the same result as processing it once.
Prerequisites
A webhook provider account (Stripe, GitHub, Shopify, or similar) with webhook delivery logs
