hn • r/hackernews
Comment on: Shopify replaced Redis with MySQL for inventory reservations–and it scaled
> Instead of one row per item with a quantity column, we use one row per sellable unit. An item with 10 units has 10 rows.> But one row per unit for all inventory would break down at scale—an item with 50,000 units across 10 locations would mean 500,000 rows, and the reserve query would slow as it scans through them. Instead, we maintain a bounded pool of available rows, capped at 1,000 per item/location combination. Reservations consume rows from this pool; a replenishment process refills it from the inventory ledger.Shouldn't I feel uncomfortable with such approach? It seems to create a back