Do customerIDs or orderIDs overlap across multiple storefronts?

Shopify Apps

Topic summary

A developer is building a Shopify app that pulls customer and order data via the API. They currently serve clients with single storefronts but now have a client with two storefronts.

Core concern: Whether customerIDs and orderIDs are globally unique across all Shopify storefronts, or only unique within individual stores.

Risk: If IDs overlap between storefronts, pulling data from multiple stores could overwrite existing records, since their database uses customerID and orderID as primary keys.

Current status: The developer has received conflicting answers from Shopify Support and is seeking confirmation from other developers before proceeding.

Note: They clarify this question is about the ID fields themselves, not Order Numbers.

The discussion remains open with one follow-up asking if the original poster found an answer about cross-store ID uniqueness.

Summarized with AI on November 12. AI used: claude-sonnet-4-5-20250929.
1

I have a public Shopify app that pulls customers and orders from the Shopify API. Typically we only pull from one storefront per-client, however we have a client with two storefronts. If we were to pull data from the second storefront, I am afraid of the possibility of overwriting data since CustomerID and OrderID are our primary keys.

Are CustomerID and OrderID unique across all of Shopify? I’ve been told different answers from Shopify Support, so I wanted to confirm findings with devs.

P.S. This is not Order Number, we are only looking at OrderID.

2

Did you find out whether customer id is unique across stores?