E-Commerce Platform

Overview

This project provides a complete backend foundation for building an e-commerce platform. It is designed to help teams quickly bootstrap a production-ready system while also serving as a deep exploration of backend engineering and system design concepts.

With this foundation in place, an e-commerce backend can be set up and extended rapidly for real-world use cases.

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Features

• API Gateway with per-user rate limiting
• User authentication and authorization
• Seller and Admin role-based access
• Product catalog management
• Cart management
• Checkout flow
• Order management
• Asynchronous notification handling

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Tech Stack

• Backend: .NET 9 / C#

• Database: PostgreSQL

• Authentication: JWT

• Caching: Redis

• Messaging:

  • Redis Pub/Sub
  • RabbitMQ

• Resilience: Polly

• Notifications: SMTP

• Build: .NET CLI

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Architecture

Modular Monolith

The system is implemented as a modular monolith to keep the initial setup simple while maintaining clear domain boundaries. This approach avoids the operational overhead of microservices for a smaller user base, while still enabling future scalability.

Each module is designed with well-defined boundaries and communicates only through interfaces, making it straightforward to extract individual modules into independent microservices if scaling requirements increase.

Core Modules

• Users
• Products
• Orders
• Notifications

Communication Model

• Synchronous (In-Process): Used for atomic transactional flows such as order placement and payment processing.
• Asynchronous: Used for inventory processing, notifications, cancellations, and other non-blocking workflows.

Infrastructure & Tooling Decisions

Redis

• Used for caching frequently accessed data
• Used as a lightweight pub/sub mechanism for internal event propagation

RabbitMQ

• Used for reliable asynchronous workflows
• Order placed and order cancelled events are published to RabbitMQ
• Payment and notification services consume these events to trigger refunds and user notifications

Polly

• Applied to external service interactions only
• Used for retry handling during refund failures and notification delivery failures
• Not used for database retries

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Security & Authentication

Authentication Model

• A single JWT-based authentication system is used
• Authorization is enforced through fine-grained role-based access control

Roles:

• Admin: Full system access
• Seller: Can manage and sell products
• User: Can browse products, place orders, and manage carts

API Gateway

• Rate limiting is applied on a per-user basis to prevent abuse

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Setup & Run

Prerequisites

• .NET 9
• PostgreSQL
• Redis
• RabbitMQ

Steps

1. Set up PostgreSQL using the provided SQL scripts

2. Configure the following values:

   • PostgreSQL credentials
   • JWT secret key
   • SMTP configuration
   • RabbitMQ configuration
   • Redis configuration

3. Run the application using the .NET CLI

4. Use Postman or Insomnia to interact with the APIs via localhost

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Phase 1 Scope

Phase 1 focuses on building the complete backend foundation required for an e-commerce platform, with an emphasis on core transactional and domain workflows.

Intentionally Excluded

• Shipment and tracking services (to keep focus on core commerce flows)
• Product image storage and management
• User profile editing

These features can be layered on top of the existing foundation without architectural changes.

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Future Work

• Shipment and tracking services
• Product image management
• User profile management
• Advanced reporting and analytics

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Project Intent

This project is intended to demonstrate a production-ready, highly scalable e-commerce backend using .NET and a modular monolith architecture.