Architecture Overview¶

Understanding the high-level design and principles that make Nexus a powerful plugin-based application platform.

🎯 Core Philosophy¶

Nexus is built on the principle that everything is a plugin. This fundamental design decision shapes every aspect of the architecture:

• Modularity First: Features are isolated, independent components
• Event-Driven: Loose coupling through asynchronous communication
• Service-Oriented: Shared functionality through service registry
• Configuration-Driven: Behavior controlled through declarative config

🏗️ High-Level Architecture¶

graph TB
    subgraph "HTTP Layer"
        A[FastAPI Application]
        B[Middleware Stack]
        C[Route Handlers]
    end

    subgraph "Core Framework"
        D[Plugin Manager]
        E[Event Bus]
        F[Service Registry]
        G[Configuration Manager]
    end

    subgraph "Plugin Ecosystem"
        H[Authentication Plugin]
        I[Database Plugin]
        J[Custom Plugins]
        K[Third-party Plugins]
    end

    subgraph "Infrastructure"
        L[Database]
        M[Cache]
        N[External APIs]
        O[File Storage]
    end

    A --> B --> C
    C --> D
    D --> H
    D --> I
    D --> J
    D --> K

    H --> E
    I --> E
    J --> E
    K --> E

    H --> F
    I --> F
    J --> F
    K --> F

    All --> G

    H --> L
    I --> L
    J --> M
    K --> N
    J --> O

🧩 Component Layers¶

1. HTTP Layer¶

Purpose: Handle incoming requests and outgoing responses - FastAPI Application: ASGI-compliant web framework - Middleware Stack: Cross-cutting concerns (CORS, auth, logging) - Route Handlers: Map URLs to plugin functionality

2. Core Framework¶

Purpose: Provide plugin infrastructure and coordination - Plugin Manager: Lifecycle management and dependency resolution - Event Bus: Asynchronous inter-plugin communication - Service Registry: Dependency injection and service discovery - Configuration Manager: Environment-specific settings

3. Plugin Ecosystem¶

Purpose: Implement business logic and features - Core Plugins: Essential framework functionality - Custom Plugins: Application-specific features - Third-party Plugins: External integrations

4. Infrastructure Layer¶

Purpose: External systems and storage - Databases: Persistent data storage - Caches: High-speed data access - External APIs: Third-party service integration - File Storage: Document and media management

🔄 Plugin Lifecycle¶

stateDiagram-v2
    [*] --> Discovery: App Startup
    Discovery --> Validation: Plugin Found
    Validation --> Loading: Manifest Valid
    Loading --> Initialization: Code Loaded
    Initialization --> Registration: initialize() Success
    Registration --> Active: Routes/Services Registered

    Active --> Active: Handle Requests
    Active --> Active: Process Events
    Active --> Active: Health Checks

    Active --> Shutdown: App Shutdown
    Shutdown --> Cleanup: shutdown() Called
    Cleanup --> [*]: Resources Released

    Validation --> Failed: Invalid Manifest
    Loading --> Failed: Import Error
    Initialization --> Failed: Initialize Error
    Failed --> [*]: Plugin Disabled

💫 Event-Driven Communication¶

sequenceDiagram
    participant A as Plugin A
    participant E as Event Bus
    participant B as Plugin B
    participant C as Plugin C

    Note over A,C: User Registration Flow

    A->>E: emit("user.registration.started")
    E->>B: notify Email Plugin
    E->>C: notify Analytics Plugin

    A->>A: Create User Record
    A->>E: emit("user.created")

    E->>B: Send Welcome Email
    E->>C: Track User Signup

    B->>E: emit("email.sent")
    C->>E: emit("analytics.tracked")

    Note over A,C: Loose coupling, scalable

🎯 Design Principles¶

1. Plugin-First Architecture¶

graph LR
    A[Monolithic Feature] --> B[Plugin Components]

    subgraph "Traditional"
        C[User Management]
        D[Email System]
        E[Analytics]
        F[All Coupled]
    end

    subgraph "Nexus Plugins"
        G[User Plugin]
        H[Email Plugin]
        I[Analytics Plugin]
        J[Event Bus]
    end

    G --> J
    H --> J
    I --> J

Benefits: - Independent development and testing - Hot-swappable components - Clear responsibility boundaries - Reusable across projects

2. Dependency Injection¶

# Service Registration
service_registry.register("email", EmailService())
service_registry.register("storage", FileStorage())

# Service Usage
class UserPlugin(BasePlugin):
    def __init__(self):
        self.email = service_registry.get("email")
        self.storage = service_registry.get("storage")

Benefits: - Testable components (easy mocking) - Configurable implementations - Runtime service switching - Clear dependency management

3. Configuration-Driven Behavior¶

plugins:
  user_manager:
    max_users: 1000
    email_verification: true

  email_service:
    provider: "sendgrid"
    templates_dir: "./templates"

Benefits: - Environment-specific behavior - Runtime reconfiguration - Non-technical user control - Deployment flexibility

🚀 Request Processing Flow¶

graph LR
    A[HTTP Request] --> B[Middleware]
    B --> C[Route Resolution]
    C --> D[Plugin Handler]
    D --> E[Business Logic]
    E --> F[Service Calls]
    F --> G[Database/APIs]
    G --> H[Event Emission]
    H --> I[Response Generation]
    I --> J[Middleware]
    J --> K[HTTP Response]

    subgraph "Plugin Execution"
        D
        E
        F
        H
    end

    subgraph "Framework Execution"
        B
        C
        I
        J
    end

📊 Scalability Patterns¶

Horizontal Scaling¶

graph TB
    LB[Load Balancer] --> A1[Nexus Instance 1]
    LB --> A2[Nexus Instance 2]
    LB --> A3[Nexus Instance N]

    A1 --> DB[(Shared Database)]
    A2 --> DB
    A3 --> DB

    A1 --> CACHE[(Shared Cache)]
    A2 --> CACHE
    A3 --> CACHE

Characteristics: - Stateless application instances - Shared data layer - Session-less design - Plugin isolation

Plugin-Level Scaling¶

graph TB
    A[Request Router] --> B[Plugin Instance Pool]

    subgraph "Plugin Pool"
        C[Plugin Instance 1]
        D[Plugin Instance 2]
        E[Plugin Instance N]
    end

    B --> C
    B --> D
    B --> E

    C --> F[Shared Services]
    D --> F
    E --> F

Benefits: - Independent plugin scaling - Resource optimization - Fault isolation - Performance tuning

🛡️ Security Model¶

graph TB
    A[Request] --> B[Rate Limiting]
    B --> C[Authentication]
    C --> D[Authorization]
    D --> E[Input Validation]
    E --> F[Plugin Execution]
    F --> G[Output Sanitization]
    G --> H[Response]

    subgraph "Security Layers"
        I[Network Security]
        J[Application Security]
        K[Data Security]
        L[Plugin Security]
    end

    B -.-> I
    C -.-> J
    D -.-> J
    E -.-> K
    F -.-> L
    G -.-> K

Key Features: - Multi-layer security validation - Plugin-level permissions - Resource access control - Audit logging

⚡ Performance Characteristics¶

Async-First Design¶

• Non-blocking I/O: All operations are async-capable
• Concurrent Processing: Multiple requests handled simultaneously
• Resource Efficiency: Optimal CPU and memory usage
• Scalable Architecture: Handles thousands of concurrent connections

Memory Management¶

• Plugin Isolation: Separate memory spaces prevent interference
• Resource Pooling: Reuse expensive objects (DB connections)
• Lazy Loading: Load resources only when needed
• Garbage Collection: Optimized for plugin lifecycle

Caching Strategy¶

graph TB
    A[Request] --> B{Cache Hit?}
    B -->|Yes| C[Return Cached]
    B -->|No| D[Plugin Processing]
    D --> E[Database Query]
    E --> F[Cache Result]
    F --> G[Return Response]

    subgraph "Cache Layers"
        H[Memory Cache]
        I[Redis Cache]
        J[Database Cache]
    end

    B -.-> H
    B -.-> I
    E -.-> J

🎯 Architecture Benefits¶

For Development Teams¶

• Parallel Development: Teams work on independent plugins
• Clear Boundaries: Well-defined interfaces and contracts
• Easy Testing: Isolated components with mocked dependencies
• Rapid Prototyping: Quick plugin creation and deployment

For Operations Teams¶

• Monitoring Ready: Built-in metrics and health checks
• Deployment Flexibility: Independent plugin deployment
• Scaling Options: Fine-grained resource allocation
• Troubleshooting: Clear component boundaries for debugging

For Business Stakeholders¶

• Feature Velocity: Faster time-to-market for new features
• Risk Reduction: Isolated failures don't affect entire system
• Cost Optimization: Pay for only what you use
• Vendor Flexibility: Easy integration switching

🚀 Next Steps¶

To dive deeper into specific aspects:

• Core Components - Detailed component architecture
• Event System - Event-driven communication patterns
• Security Model - Security architecture and best practices
• Plugin Development - Build plugins with this architecture

This architecture enables building complex, scalable applications while maintaining simplicity through the plugin system.