Design an E-Commerce Checkout & Inventory System
Process high-scale e-commerce orders: Distributed cart management, atomic inventory decrementing, idempotent payment settlement, and Saga order fulfillment.
01.1. Functional & Non-Functional Requirements
An E-Commerce Checkout and Inventory System processes customer shopping carts into finalized orders, manages real-time warehouse stock levels, charges payments safely, and dispatches fulfillment jobs.
Functional Requirements
- Shopping Cart: Add, update, and persist items in multi-device carts.
- Atomic Inventory Deduction: Deduct stock atomically during checkout; never allow overselling of inventory.
- Idempotent Payment Settlement: Ensure customers are charged exactly once, even during network drops, double-clicks, or automated retries.
- Order State Lifecycle: Support order progression:
PENDING_PAYMENT→PAID→PROCESSING→SHIPPED→DELIVERED(orCANCELLED/REFUNDED).
Non-Functional Requirements
- Absolute Inventory Consistency (Zero Overselling): If 10 items are in stock, exactly 10 orders can be completed.
- High Concurrency & Flash Sale Resilience: Handle Black Friday / Prime Day surges (
50,000 checkout QPS) without deadlocks. - Idempotency Guarantee: Duplicate checkout submissions with the same key produce identical responses without duplicate financial charges.
E-Commerce Checkout & Saga Order Fulfillment Pipeline 🛍️
E-Commerce Checkout & Saga Order Fulfillment Pipeline 🛍️
Saga orchestrator coordinating distributed atomic inventory reservation, idempotent payment settlement, compensating rollbacks, and asynchronous fulfillment events.
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