Architecture

This guide provides an overview of the ReqFlow system architecture, explaining how the different components work together to provide a robust requisition management solution.

System Overview

ReqFlow is built on a modern, scalable architecture designed to handle the complexities of enterprise requisition management. The system consists of several key components:

┌─────────────────────────────────────────────────────────┐
│                      Client Applications                    │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────────┐  │
│  │  Web Client  │  │ Mobile Apps  │  │ Integration APIs │  │
│  └──────────────┘  └──────────────┘  └──────────────────┘  │
└─────────────────────────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────┐
│                      API Gateway                         │
└─────────────────────────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────┐
│                   Microservices Layer                    │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐   │
│  │ Requisition  │  │   Approval   │  │   Payment    │   │
│  │   Service    │  │   Service    │  │   Service    │   │
│  └──────────────┘  └──────────────┘  └──────────────┘   │
│                                                         │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐   │
│  │    User      │  │  Document    │  │  Reporting   │   │
│  │   Service    │  │   Service    │  │   Service    │   │
│  └──────────────┘  └──────────────┘  └──────────────┘   │
└─────────────────────────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────┐
│                      Data Layer                          │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐   │
│  │  Relational  │  │   Document   │  │    Cache     │   │
│  │   Database   │  │   Storage    │  │              │   │
│  └──────────────┘  └──────────────┘  └──────────────┘   │
└─────────────────────────────────────────────────────────┘

Key Components

Client Applications

The user-facing interfaces that allow interaction with the ReqFlow system. These include:

Web application (React-based responsive interface)
Mobile applications (iOS and Android)
Integration APIs for third-party systems

API Gateway

A centralized entry point for all client requests, handling:

Authentication and authorization
Request routing
Rate limiting
API versioning

Microservices Layer

A collection of specialized services that handle specific business functions:

Requisition Service: Manages requisition creation, updates, and lifecycle
Approval Service: Handles approval workflows and notifications
Payment Service: Processes payments and integrates with financial systems
User Service: Manages user accounts, roles, and permissions
Document Service: Handles document storage, retrieval, and versioning
Reporting Service: Generates reports and analytics

Data Layer

The persistence layer that stores all system data:

Relational Database: Stores structured data like user accounts and requisitions
Document Storage: Manages unstructured data like invoices and attachments
Cache: Improves performance by storing frequently accessed data

Communication Patterns

ReqFlow uses a combination of synchronous and asynchronous communication patterns:

REST APIs: Used for direct client-to-service communication where immediate responses are required.
Event-driven messaging: Used for asynchronous communication between services, enabling loose coupling and improved scalability.
WebSockets: Used for real-time notifications and updates to clients.

Deployment Architecture

ReqFlow is designed to be deployed in a cloud environment, with the following characteristics:

Containerization: All services are containerized using Docker for consistent deployment across environments.
Orchestration: Kubernetes is used for container orchestration, providing automated deployment, scaling, and management.
Infrastructure as Code: All infrastructure is defined and managed using Terraform, ensuring consistency and reproducibility.
CI/CD: Continuous Integration and Continuous Deployment pipelines automate the testing and deployment process.

Security Architecture

Security is a core consideration in the ReqFlow architecture:

Authentication: OAuth 2.0 and OpenID Connect for secure user authentication.
Authorization: Role-based access control (RBAC) with fine-grained permissions.
Data Encryption: All data is encrypted both in transit (TLS) and at rest.
API Security: API keys, rate limiting, and input validation protect against common attacks.
Audit Logging: Comprehensive logging of all system actions for security and compliance.