By the way there is counter_culture[1] which is great for more complex counter caches: Inventory: product quantity 1 2 1 5 2

By the way there is counter_culture[1] which is great for more complex counter caches: Inventory: product quantity 1 2 1 5 2 -1 2 3 2 10 And having a counter cache for the sum per product (e.g.: product.inventory_quantity). [1]: https://github.com/magnusvk/counter_culture https://github.com/magnusvk/counter_culture