SmartLoanSystem

SmartLoanSystem is a robust, distributed backend architecture designed to handle loan applications through automated workflows and decoupled business rules. This project demonstrates advanced software engineering patterns, including Event-Driven Architecture (EDA), Workflow Orchestration, and the Decision Model and Notation (DMN) standard.

🏗️ Architecture & Design

The system is built on SOLID principles to ensure maintainability and extensibility:

• Event-Driven Communication: Services communicate asynchronously using MassTransit and RabbitMQ, ensuring high availability and loose coupling.

• Workflow Orchestration: Loan processing is managed by Elsa Workflows 3.0, allowing for long-running processes and complex state management.

• Externalized Rules (DMN): Loan approval logic is decoupled from the application code using a DMN engine. This allows business analysts to modify rules (e.g., salary thresholds) without redeploying services.

• Idempotency & Performance: Implements Redis caching to detect and prevent duplicate loan requests, ensuring system reliability.

🚀 Tech Stack

• Framework: .NET 10.0 (C#)

• Orchestration: Elsa Workflows 3.5

• Messaging: MassTransit with RabbitMQ

• Business Rules: DMN (Decision Model and Notation)

• Database: SQL Server (Entity Framework Core)

• Caching: Redis (StackExchange.Redis)

• Containerization: Docker Compose

📂 Project Structure

• Loan.API: The gateway for submitting loan requests via REST endpoints.

• Loan.Processor: A worker service that consumes messages, executes the LoanApprovalWorkflow, and evaluates DMN rules.

• Loan.Contracts: Shared library containing records and message schemas to ensure type safety across services.

🛠️ Business Logic (DMN)

The system currently uses a DMN table to evaluate loan eligibility based on the applicant's salary:

• Input: Salary

• Rule: If Salary > 1000, the loan is marked as Approved.

• Rule: If Salary <= 1000, the loan is marked as Rejected.

🚦 Getting Started

Prerequisites

• Docker Desktop

• .NET 10 SDK

Setup

1. Clone the repository:

git clone https://github.com/absamrah/SmartLoanSystem.git

2. Configure Environment: Create a .env file in the root directory (refer to .env.example):

SQL_PASSWORD=YourStrongPassword!
RABBIT_USER=guest
RABBIT_PASS=guest

3. Run Infrastructure: Use Docker Compose to spin up SQL Server, RabbitMQ, and Redis:

docker-compose up -d

4. Run the Services: Start both the API and the Processor via your IDE or CLI.