rush shopping

Various constrains

1. Stock of items.

• Oversold to a certain extent is permitted.
• Oversold is not permitted.

2. Cart.
3. Order.

• Items in one cart should be ordered together, or not.
• Items in one cart could be split if stock of some items is insufficient.

4. Pay, money should keep strong consistency.

front-end web service

back-end key-value store

offline batch analysis