Fintech & Commerce

Design Amazon (Cart and Checkout systems)

An e-commerce cart and checkout flow coordinating inventory reservation, pricing, and payment as a single reliable distributed transaction.

Core Architectural Components

Session-based, persistent cart state synced across devices.

Holds stock for a cart item so it can't be sold out from under the buyer at checkout.

Applies discounts, coupons, and dynamic pricing at checkout time.

A saga/workflow coordinating inventory, pricing, and payment as one logical transaction.

Authorizes and captures payment as part of the checkout saga.

Owns the order record once checkout succeeds, driving fulfillment.

Computes final line-item costs before the charge is authorized.