System requirements

Functional:

1. User Registration and Authentication: Users should be able to sign up and log in to the platform.
2. Coupon Code Retrieval: The service must automatically find and apply coupon codes during checkout.
3. Price Comparison: The system should enable users to compare prices across various online retailers.
4. Deal Alerts: Users should have the option to set alerts for specific products or categories for deals and coupons.
5. Rewards Program: The service should offer a rewards program to encourage user engagement, allowing users to earn points for using the service.
6. User Profile Management: Users must be able to manage their profiles, preferences, and notification settings.

Non-Functional:

1. Performance: The system should handle at least 10,000 concurrent users during peak times without significant performance degradation.
2. Scalability: The architecture should be scalable to support a growing number of users and transactions.
3. Security: User data must be secured using encryption techniques, especially sensitive information such as passwords.
4. Usability: The interface should be user-friendly, ensuring users can easily find and apply coupons.
5. Availability: The system should maintain an uptime of 99.9% to ensure users can access it whenever they need.

Capacity estimation

Estimate the scale of the system you are going to design...

API design

Based on these functionalities, we can define the following core APIs:

User Management APIs

• User Registration:
• POST /users
• Parameters: user details (name, email, password, etc.)
• User Login:
• POST /auth/login
• Parameters: credentials (email, password)
• Returns: authentication token
• User Profile Update:
• PUT /users/{userId}
• Parameters: updated user details
• User Preferences Update:
• PUT /users/{userId}/preferences
• Parameters: updated user preferences (e.g., categories, brands)

Coupon Management APIs

• Coupon Retrieval:
• GET /coupons?storeId={storeId}&productId={productId}
• Returns: list of applicable coupons
• Coupon Application:
• POST /coupons/apply
• Parameters: coupon code, order details
• Returns: updated order total
• Coupon Validation:
• POST /coupons/validate
• Parameters: coupon code, order details
• Returns: validation status

Price Comparison APIs

• Product Search:
• GET /products?query={query}
• Returns: list of products with prices from different retailers
• Price History:
• GET /products/{productId}/priceHistory
• Returns: price history for a product

Deal Alerts APIs

• Subscribe to Alerts:
• POST /alerts/subscribe
• Parameters: user ID, product/category preferences
• Unsubscribe from Alerts:
• DELETE /alerts/unsubscribe
• Parameters: user ID, alert ID

Rewards Program APIs

• Earn Points:
• POST /rewards/earn
• Parameters: user ID, action (e.g., coupon applied, purchase made)
• Redeem Rewards:
• POST /rewards/redeem
• Parameters: user ID, reward ID
• Reward Catalog:
• GET /rewards/catalog
• Returns: list of available rewards

Database design

Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...

High-level design

1. User Interface (UI):
2. A web and mobile application interface to allow users to interact with the service.
3. Feature sections include coupon search, deals, price comparison, user profile, etc.
4. Database: A relational or NoSQL database to store user data, coupon information, product details, and transaction logs.
5. Web Scraper / Data Aggregator: A system to scrape coupon codes from various online retailers and aggregate prices for comparison.
6. Notification Service: A service to send alerts to users about new deals or reward updates.
7. User Service: Handles user registration, authentication, profile management, and preferences.
8. Coupon Service: Manages coupon creation, retrieval, application, and validation.
9. Price Comparison Service: Compares product prices across different retailers.
10. Deal Alert Service: Manages user subscriptions, sends notifications, and tracks deal history.
11. Reward Service: Manages user points, rewards, and redemption.

Request flows

Let's detail the request flow scenario for a user applying a coupon code during an online shopping checkout on your Online Coupon Service. This will illustrate how the various components interact to fulfill the user’s request.

Request Flow Scenario: Applying a Coupon Code

1. User Initiates Checkout: The user selects items for purchase and starts the checkout process on an e-commerce site.
2. Request for Coupons: The user clicks on the browser extension or app to find available coupons.
3. Send Coupon Request: The UI sends a request to the Backend Service to retrieve applicable coupon codes for the items in the user's cart.
4. Backend Service Processing: The Backend Service processes the request, first checking the Database for applicable coupons. If no relevant coupons are found, it sends a request to the Web Scraper to find fresh coupons.
5. Data Retrieval: The Web Scraper collects coupon data from various online retailers and returns it to the Backend Service. The Backend Service stores this new coupon information back in the Database for future reference.
6. Send Coupons to User: The Backend Service sends the list of applicable coupons back to the User Interface.
7. User Applies Coupon: The user selects a coupon from the presented list, which is then applied during the checkout process.
8. Confirmation and Notification: The system confirms the application of the coupon, updates the price, and optionally sends a notification to the user via the Notification Service.

Detailed component design

Let's break down the detailed component design for each major part of the Online Coupon Service, including their responsibilities and interactions.

1. User Interface (UI)

Responsibilities:

• Provide a user-friendly interface on web and mobile platforms.
• Allow users to search for coupons, manage their profiles, and view rewards.
• Display real-time notifications regarding deals and applied coupons.

Components:

• Web Application: Built using frameworks like React or Angular.
• Mobile Application: Native applications for iOS and Android or a hybrid solution using Flutter or React Native.
• Browser Extension: A lightweight extension that logs user activity and provides a quick way to apply coupons during checkout.

2. Backend Service

Responsibilities:

• Handle all business logic related to user requests, including coupon searching and rewards calculation.
• Ensure secure communication and data processing.

Components:

• API Gateway: Manages all incoming requests and routes them to the appropriate services (e.g., Express.js for Node.js).
• Authentication Service: Handles user registration and authentication (using OAuth, JWT, etc.)
• Coupon Management Service: Processes requests for coupon retrieval, validation, and application.
• User Management Service: Manages user profiles, rewards, and settings.

3. Database

Responsibilities:

• Store user data, coupon details, transaction records, and product information securely.

Components:

• Relational Database (like PostgreSQL or MySQL) for structured data (users, transactions).
• NoSQL Database (like MongoDB) for flexible schema data like coupons from different retailers.

4. Web Scraper / Data Aggregator

Responsibilities:

• Periodically scrape data from various e-commerce websites to gather coupon codes and pricing information.

Components:

• Scraping Engine: A service using libraries like BeautifulSoup (Python) or Puppeteer (Node.js).
• Scheduler: A cron job or service that triggers scraping at defined intervals.
• Data Processing Pipeline: Validate and normalize scraped data before storing it in the database.

5. Notification Service

Responsibilities:

• Deliver real-time updates and alerts to users about new deals, coupons, or rewards.

Components:

• WebSockets: Real-time communication protocol for sending live updates to the UI.
• Email/SMS Service: For sending non-instantaneous notifications (using services like SendGrid or Twilio).
• Notification Queue: A message queue (e.g., RabbitMQ or AWS SQS) to manage and buffer notifications.

Detailed Component Interaction Diagram

Now, let’s visualize these interactions within the overall architecture:

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?