Design Online Shopping System like Amazon
Design an Online Shopping System like Amazon that supports product browsing, cart management, order placement, payment processing, and inventory tracking across multiple sellers.
An Online Shopping System is a large-scale e-commerce platform that enables users to browse, search, and purchase products from a wide range of categories, all from the convenience of a digital interface.
Products are often sold by multiple sellers, with the platform acting as a central hub for managing listings, payments, logistics, and order fulfillment.
In this chapter, we will explore the low-level design of online shopping system like Amazon in detail.
Let's start by clarifying the requirements:
1. Clarifying Requirements
Before starting the design, it's important to ask thoughtful questions to uncover hidden assumptions and better define the scope of the system.
Here is an example of how a conversation between the candidate and the interviewer might unfold:
Candidate: Should the system support both buyers and sellers, or are we focusing only on the customer-facing side for now?
Interviewer: Let’s focus on the customer-facing side. You can assume that the product catalog is already populated by sellers.
Candidate: Should we support product categories, filters, and search functionality for browsing the catalog?
Interviewer: Yes, users should be able to search products by name and apply filters such as category, price range, brand, and rating.
Candidate: Do we need to support features like cart management and order history?
Interviewer: Yes, customers should be able to add products to their cart, remove them, and view past orders.
Candidate: Should we handle real-time inventory updates and stock validation during checkout?
Interviewer: Yes, the system should validate inventory before confirming an order and update it accordingly after the purchase.
Candidate: Are we implementing payment processing and delivery tracking?
Interviewer: For this version, assume payment is handled externally and is always successful. Delivery tracking is not required.
Candidate: Should we allow users to leave reviews and ratings for products?
Interviewer: Not in this version. Let’s skip reviews and focus on browsing, ordering, and cart management.
After gathering the details, we can summarize the key system requirements.
1.1 Functional Requirements
- Allow users to browse and search products with filters (category, price, brand, rating)
- Enable users to view product details (title, description, price, availability)
- Support adding and removing items in a shopping cart
- Allow users to place orders from items in the cart
- Validate inventory before confirming orders and update stock upon purchase
- Allow users to view their past orders and order details
- Support user authentication (login, registration, logout)
- Provide a unique order ID for each successful transaction
1.2 Non-Functional Requirements
- Modularity: The system should include well-separated components such as CatalogService, CartService, OrderService, and UserService
- Scalability: The system should support high volumes of product listings, concurrent users, and transactions
- Extensibility: The design should allow for future features like seller dashboards, product reviews, wishlists, and delivery tracking
- Availability: The core services (catalog browsing, cart, order placement) should be highly available
- Consistency: Inventory and order placement should be transactionally consistent to avoid overselling
- Maintainability: The code should be organized, testable, and easy to extend
- Security: User data (profile, order history) should be access-controlled and securely stored