Hydrogen with Shopify Webhooks for Inventory Sync

You should subscribe to the `inventory_level_update` webhook topic, which fires whenever stock levels change in the Shopify admin. Your Hydrogen app (built on Remix) can handle this in a resource route action and use it to invalidate or update the relevant cached product queries.

Shopify sends an `X-Shopify-Hmac-SHA256` header with each webhook delivery that you verify using your app's API secret key via HMAC. In Hydrogen, you perform this verification inside your Remix action handler before trusting or processing the incoming JSON payload.

Yes, since Hydrogen is a server-rendered Remix application, webhook routes can be handled directly as Remix resource routes without a separate service. You register the route URL in your Shopify Partners dashboard under app webhook subscriptions, and the route runs on whatever host serves Hydrogen (e.g., Shopify Oxygen).

When the webhook fires, your Hydrogen action can call Remix's data-deletion or revalidation helpers to purge stale inventory data from the server-side cache. This ensures that subsequent page loads or API fetches for affected products reflect the updated stock count without requiring a full site rebuild.