How to Build a Production-Safe WhatsApp Webhook Handler in Node.js

Developers integrating Meta's WhatsApp Business Cloud API face a critical pitfall known as the Webhook Retry Trap, where slow server responses cause Meta to resend duplicate events over several days. Meta enforces a strict 3-second response timeout, and any delay — from database calls or external APIs — triggers exponential backoff retries that can flood systems with duplicate messages. A resilient architecture decouples webhook ingestion from business logic using a durable queue, such as Redis or AWS SQS, returning an immediate 200 OK while processing happens asynchronously. Cryptographic signature validation via HMAC SHA-256 is essential to block forged payloads, with a key caution that Node.js's timingSafeEqual throws a RangeError if compared buffers differ in length. An idempotency gate checking unique message IDs prevents duplicate processing even when retries do occur.