title: Item level tracking in Shopify
body: <p>Could you please specify, what is the correct way to track the quantity of the variants of items in stock?</p>
  <p>I see that <code>products/update</code> webhook shows the quantity, but I'm not sure if it fires when an item is purchased (and its quantity reduces by one), and in case of <code>inventory_items/update</code> there's no quantity information (though it seems I can thract it using  <code>InventoryLevel</code> API call), but I'm not sure if this notification launches after item purchase.</p>