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E-CommerceApp.md

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System Design: E-Commerce Website

Problem Statement

Design a large-scale e-commerce platform where users can browse products, add them to their cart, make purchases, and receive order notifications. The system should handle a large number of concurrent users and support various features like product recommendations, order management, and payments.

Requirements

Functional Requirements:

  1. User Registration and Authentication: Users should be able to sign up, log in, and manage their profiles.
  2. Product Catalog: Display a catalog of products with details like price, description, availability, and reviews.
  3. Search and Filtering: Allow users to search for products and apply filters (price range, category, ratings, etc.).
  4. Cart Management: Users can add products to a cart, remove items, and update quantities.
  5. Order Placement: Users can place an order with the items in their cart and proceed to checkout.
  6. Payment Processing: Handle secure payments via credit/debit cards, digital wallets, or bank transfers.
  7. Order Management: Allow users to view order history and track order status (processing, shipped, delivered).
  8. Product Reviews and Ratings: Users can leave ratings and reviews for products they’ve purchased.
  9. Inventory Management: The system should track the stock of each product and prevent over-ordering.
  10. Notifications: Send users notifications about orders, shipping updates, and promotions.

Non-Functional Requirements:

  1. Scalability: The system should handle millions of users, product listings, and concurrent transactions.
  2. High Availability: Ensure the system is available 24/7 with minimal downtime.
  3. Low Latency: Provide fast response times for product searches, adding items to the cart, and placing orders.
  4. Data Security: Ensure secure handling of user data, payment information, and order details.
  5. Reliability: Ensure orders are processed correctly, and inventory is updated accurately in real time.

Components of the System

The e-commerce system can be broken down into the following key components:

  1. User Service: Manages user registration, authentication, and profile management.
  2. Product Catalog Service: Stores and retrieves product details like pricing, availability, and descriptions.
  3. Search and Filtering Service: Allows users to search for products by category, name, and filters.
  4. Cart Service: Manages user carts and their contents, enabling users to add or remove products.
  5. Order Service: Handles order creation, processing, and order history.
  6. Payment Service: Integrates with payment gateways to securely process payments.
  7. Inventory Management Service: Manages product stock levels and updates inventory after purchases.
  8. Notification Service: Sends order confirmations, shipping updates, and promotional messages to users.
  9. Recommendation Engine: Provides personalized product recommendations based on user preferences, behavior, and browsing history.
  10. Review and Rating Service: Stores and displays user reviews and ratings for products.

High-Level Design

  1. User Interface (UI): Users interact with the platform through a web or mobile app, where they can browse products, search, add items to their cart, and complete purchases.
  2. API Layer: Provides APIs for user registration (POST /register), product search (GET /search), adding items to the cart (POST /cart/add), placing orders (POST /order), and payment processing (POST /pay).
  3. Service Layer:
    • User Service: Handles user registration, login, and profile management.
    • Product Catalog Service: Retrieves product details and pricing.
    • Search Service: Handles search queries and filtering based on product attributes (category, price, brand).
    • Cart Service: Manages adding and removing items from the user’s cart.
    • Order Service: Manages order creation, processing, and tracking.
    • Payment Service: Securely processes payments via third-party payment gateways.
    • Inventory Management: Tracks product stock levels and ensures accurate order fulfillment.
    • Notification Service: Sends email and SMS notifications for order updates.
  4. Storage Layer:
    • Database: Stores user profiles, product details, order information, and transaction history.
    • Cache: Stores frequently accessed data like product details and cart contents for faster access.
    • Blob Storage: Stores media assets like product images, videos, and promotional banners.

Detailed Design

1. User Registration and Authentication

Users register using email or phone, and they can log in to manage their profile, shipping addresses, and payment methods.

Database Schema for Users:

Field Type Description
user_id String (PK) Unique identifier for the user.
username String Unique username chosen by the user.
email String User’s email address.
phone_number String User’s phone number.
password_hash String Hashed password for secure login.
addresses JSON List of saved shipping addresses.
payment_methods JSON Saved credit/debit card or digital wallet details.

Key Operations:

  • Registration/Login: Users can register and log in using email/phone or third-party OAuth (Google, Facebook).
  • Profile Management: Users can update their profile, shipping addresses, and payment methods.

2. Product Catalog Management

The product catalog contains information about all the items available on the platform, including their price, availability, and description.

Product Catalog Schema:

Field Type Description
product_id String (PK) Unique identifier for the product.
name String Name of the product.
description Text Description of the product.
price Float Price of the product.
category String Category the product belongs to (e.g., electronics, clothing).
inventory_count Integer Number of items in stock.
rating Float Average user rating for the product.
media_url String URL of the product image or video.

3. Search and Filtering

Users can search for products by name, category, or attributes (e.g., price range, rating). The search results can be filtered based on various criteria like price, rating, and availability.

Search Flow:

  1. User enters a search query (e.g., "smartphone").
  2. The system retrieves matching products from the catalog service and applies filters.
  3. Results are ranked by relevance and returned to the user.

4. Cart Management

Users can add products to their cart, adjust quantities, or remove items. The cart service ensures that the cart contents persist across user sessions.

Cart Schema:

Field Type Description
cart_id String (PK) Unique identifier for the cart.
user_id String (FK) ID of the user who owns the cart.
product_id String (FK) ID of the product in the cart.
quantity Integer Quantity of the product in the cart.

5. Order Placement and Tracking

Users can place orders with the items in their cart. The system processes the order, reduces inventory, and sends confirmation notifications. Users can also track the status of their orders.

Order Schema:

Field Type Description
order_id String (PK) Unique identifier for the order.
user_id String (FK) ID of the user placing the order.
product_list Array[JSON] List of products in the order.
total_amount Float Total amount for the order.
status String Order status (processing, shipped, delivered).
shipping_address JSON Shipping address for the order.

6. Payment Processing

The system integrates with third-party payment gateways (e.g., Stripe, PayPal) to process payments securely.

Payment Flow:

  1. User proceeds to checkout and selects a payment method (credit card, wallet).
  2. The payment gateway handles the transaction and returns a confirmation.
  3. The order is placed after the payment is successful.

Payment Schema:

Field Type Description
payment_id String (PK) Unique identifier for the payment.
order_id String (FK) ID of the order being paid for.
amount Float Total amount paid for the order.
payment_method String Payment method (credit card, PayPal, etc.).
status String Payment status (successful, failed).

7. Inventory Management

The system tracks inventory for each product and updates the stock after an order is placed.

Inventory Flow:

  1. When an order is placed, the inventory for the ordered products is reduced.
  2. If stock is insufficient, the system prevents over-ordering and notifies the user that the item is out of stock.

8. Notifications

The system sends email or SMS notifications for order confirmations, shipping updates, and promotions.

Notification Schema:

Field Type Description
notification_id String (PK) Unique identifier for the notification.
user_id String (FK) ID of the user receiving the notification.
message String Notification message.
timestamp Timestamp Time when the notification was sent.

Key Challenges

1. Scalability

  • The system must handle millions of users, products, and transactions concurrently.
    • Solution: Use horizontal scaling for services like the product catalog, user service, and order management.

2. Inventory Management

  • Prevent over-ordering by ensuring inventory is updated in real-time after purchases.
    • Solution: Use distributed locks or atomic transactions to prevent race conditions when updating inventory.

3. High Availability

  • Ensure the platform is available 24/7 with minimal downtime, especially during high-traffic events (e.g., Black Friday sales).
    • Solution: Use load balancers, replication, and failover mechanisms for critical services.

4. Security

  • Ensure secure handling of user data and payments.
    • Solution: Use encryption (e.g., HTTPS, TLS) and integrate with secure payment gateways (PCI-DSS compliant).

5. Search Performance

  • Search and filtering should be efficient, even with millions of products.
    • Solution: Use search engines like Elasticsearch to index and query product data.

Advanced Features (Optional)

1. Product Recommendations

  • Use a recommendation engine to suggest products based on user browsing history, past purchases, or trends.

2. Promotions and Discounts

  • Allow users to apply discount codes or promotions at checkout.

3. Multi-Warehouse Support

  • Support for multiple warehouses and shipping locations to reduce shipping times.

4. Real-Time Stock Updates

  • Display real-time inventory status on product pages to improve user experience.

Data Flow

1. Browsing and Searching Products

  • User browses the product catalog and applies filters to find relevant items.
  • The search service retrieves matching products and displays them to the user.

2. Placing an Order

  • User adds items to the cart and proceeds to checkout.
  • The order service creates the order, processes the payment, and updates the inventory.
  • The user receives an order confirmation and shipping notifications.

3. Inventory Updates

  • After an order is placed, the inventory management service updates the stock levels for the ordered products.

Scaling the System

1. Horizontal Scaling

  • Scale the product catalog, user service, and order service horizontally to handle high traffic.

2. Caching

  • Use caching (e.g., Redis) for frequently accessed data like product listings and cart contents to reduce database load.

3. Sharding

  • Shard the product catalog and order database to distribute the load across multiple servers.

4. Content Delivery Network (CDN)

  • Use a CDN to cache and deliver product images, videos, and other media content to users with low latency.

Conclusion

Designing an e-commerce website involves handling large volumes of traffic, managing inventory in real-time, and ensuring secure transactions. By leveraging microservices, horizontal scaling, caching, and secure payment gateways, the system can efficiently serve millions of users while providing a smooth shopping experience.

Further Reading