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Design an E-Commerce Shopping Website

J.P. MorganSoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenSystem Design

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This problem tests your ability to design a scalable, consistent backend architecture for an e-commerce platform, focusing on inventory management, order processing, and high-read traffic handling.

Problem Statement

Design a backend architecture for a high-traffic e-commerce shopping website (similar to Amazon or eBay). The system must handle millions of users and high concurrency during peak sale events.

Functional Requirements

  1. Users can browse products and view detailed pages.
  2. Users can add items to their shopping cart.
  3. Users can place an order, which decrements inventory.

Non-Functional Requirements

  1. Consistency: Inventory must never drop below zero; overselling is not allowed.
  2. Scalability: The system must handle sudden traffic spikes (e.g., Black Friday).
  3. Reliability: Order placement must be idempotent to prevent duplicate charges or shipments.

Deliverables

  • Provide a high-level architectural diagram (describe components like Load Balancers, API Gateways, Services, and Databases).
  • Define the database schema or storage strategy for Products, Inventory, and Orders.
  • Explain how you would handle the 'hot product' problem where thousands of users try to buy the same item simultaneously.
  • Describe the API flow for placing an order, including how you ensure idempotency.

Hints

Hint 1

Consider the trade-off between using a relational database (ACID compliance) versus a NoSQL database for inventory management at scale.

Hint 2

Think about using a distributed lock or a message queue system to serialize orders for highly contested inventory items.

Hint 3

To handle read-heavy traffic for product browsing, consider implementing caching strategies like Redis or a Content Delivery Network (CDN).

Follow-up questions

  • How would you handle a distributed transaction across multiple microservices (e.g., Inventory, Payment, and Shipping) without using 2-Phase Commit?
  • If the database becomes a bottleneck during a flash sale, what architectural changes would you implement to offload read/write pressure?
  • How would you design a feedback loop to notify the user of their order status (e.g., 'Processing', 'Confirmed', 'Out of Stock') asynchronously?