Do customerIDs or orderIDs overlap across multiple storefronts?

[kogden]

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.