136Design Amazon/Flipkart checkout: pricing, cart synchronization, payments, and failure recovery
hardAbout 60 minutesSystem designcheckoutpaymentsidempotencye-commercesystem-design
Problem
Design the frontend of an e-commerce cart and checkout like Amazon or Flipkart:
- a cart that stays in sync across devices and tabs, including for guests who later log in;
- prices, discounts, taxes and delivery charges that are always correct, even when prices or stock change during checkout;
- address and delivery-slot selection, payment with cards, UPI and wallets, including redirects to banks or apps;
- no double charges and no lost orders when users double-click, refresh, lose the network or return from a payment app;
- a fast, trustworthy experience during a big sale with heavy traffic.
Step-by-step
The server owns prices, stock, discounts and the final total. The client shows them, collects choices, and never computes the amount that will be charged.
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What's inside
- Step-by-step
- Requirements
- Architecture
- Data model and state
- Key flows and trade-offs
- Performance and reliability
- Follow-up questions
Includes 2 code listings, 4 follow-up questions.
One-time payment by UPI, card or net banking. Launch price.