Subscribe a Shopify webhook to a Google Cloud Pub/Sub topic using the pubSubWebhookSubscriptionCreate Admin GraphQL mutation

In-depth guide

Steps

1. In Google Cloud, create a Pub/Sub topic and grant the Shopify service account (`shopify-pubsub@shopify-tiers.iam.gserviceaccount.com`) the `pubsub.topics.publish` IAM role on the topic
2. Call `pubSubWebhookSubscriptionCreate(topic: ORDERS_CREATE, webhookSubscription: { pubSubProject: "my-gcp-project", pubSubTopic: "shopify-orders", format: JSON, includeFields: ["id", "email", "total_price"] })` with `write_fulfillments` or the appropriate topic-scoped scope
3. Alternatively, in API version 2025-10+, use the unified `webhookSubscriptionCreate` mutation with `uri: "pubsub://my-gcp-project:shopify-orders"` instead of the dedicated pubSub mutation
4. Verify the subscription was created by querying `webhookSubscriptions(first: 10, topics: [ORDERS_CREATE])` and confirming your Pub/Sub topic appears
5. In your Cloud Function or Pub/Sub subscriber, base64-decode the incoming message `data` field to access the Shopify webhook payload, and validate the `X-Shopify-Hmac-Sha256` header if the message is forwarded via an intermediary
6. Subscribe to the `webhook_failures` topic or set up Dead Letter Topics in Pub/Sub to catch any delivery failures