expression
as soon as it runs out; once it's gone
Used when something (stock, supplies, time) is exhausted and an action follows immediately. Often seen in notices or instructions.
商品がなくなり次第、販売を終了します。
Sales will end as soon as the product runs out.
材料がなくなり次第、料理の提供をやめます。
We will stop serving the dish once the ingredients are gone.
Compound of なくなり (continuative form of なくなる 'to run out') + 次第 (しだい, 'as soon as').