Shop-owned timed sessions carry SKU activity items with their own reserved
inventory and per-customer limit. Checkout resolves eligibility on the server,
locks candidate items by primary key after the SKU locks, and splits a cart line
into an activity-priced item plus a standard-priced remainder, so every unit
price snapshot is honest and a customer cannot exceed the limit.
Reserved activity stock and SKU stock decrement together under guards, and a
pending-payment cancellation restores both plus any redeemed coupon. Coupons are
rejected on a shop order that applied activity pricing, and a SKU cannot join
two overlapping enabled sessions.
The overlap check against group buying is present but dormant: that capability
lands later, so the check activates only once its table exists.
Surfaces (shop-admin, mall) and seeding follow.
james
393e7f7209