What is the difference between inventory_source_item and inventory_stock_x?

Question

With Magento's new multi-source inventory system, various new tables have been introduced into the database.

inventory_source_item contains the machine name of the source, SKU, quantity, and the status.

inventory_stock_x is a table that exists for each source, containing the SKU, quantity, and if it's salable.

Why does the second table exist, when the first could store all of that information?

Answer 1

inventory_source_item

Contains inventory levels for each source. A source is a physical location (like a warehouse).

inventory_stock_x

Contains aggregated levels for each stock. A stock can consists of one or many sources.

For example, you can have 3 warehouses (sources) in GB and one stock called "Great Britain" which would sum up all your warehouses in the inventory_stock_x table.