E-commerce · 8 min · 2026-08-05
Designing Cart and Inventory Systems
Reservation windows, oversell prevention and cart expiry without painful edge cases.
Carts are temporary claims on scarce stock.
Define reservation windows, expire abandoned carts, and reconcile payment success with inventory commits. Oversell usually comes from optimistic reads without a hard commit step.
Document the sad paths: partial payment, double submit, and delayed webhooks.