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docs/Developer Guide/Architecture/README.md

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+# Trilium Architecture Documentation
+
+This comprehensive guide documents the architecture of Trilium Notes, providing developers with detailed information about the system's core components, data flow, and design patterns.
+
+## Table of Contents
+
+1. [Three-Layer Cache System](Three-Layer-Cache-System.md)
+2. [Entity System](Entity-System.md) 
+3. [Widget-Based UI Architecture](Widget-Based-UI-Architecture.md)
+4. [API Architecture](API-Architecture.md)
+5. [Monorepo Structure](Monorepo-Structure.md)
+
+## Overview
+
+Trilium Notes is built as a TypeScript monorepo using NX, featuring a sophisticated architecture that balances performance, flexibility, and maintainability. The system is designed around several key architectural patterns:
+
+- **Three-layer caching system** for optimal performance across backend, frontend, and shared content
+- **Entity-based data model** supporting hierarchical note structures with multiple parent relationships
+- **Widget-based UI architecture** enabling modular and extensible interface components
+- **Multiple API layers** for internal operations, external integrations, and real-time synchronization
+- **Monorepo structure** facilitating code sharing and consistent development patterns
+
+## Quick Start for Developers
+
+If you're new to Trilium development, start with these sections:
+
+1. [Monorepo Structure](Monorepo-Structure.md) - Understand the project organization
+2. [Entity System](Entity-System.md) - Learn about the core data model
+3. [Three-Layer Cache System](Three-Layer-Cache-System.md) - Understand data flow and caching
+
+For UI development, refer to:
+- [Widget-Based UI Architecture](Widget-Based-UI-Architecture.md)
+
+For API integration, see:
+- [API Architecture](API-Architecture.md)
+
+## Architecture Principles
+
+### Performance First
+- Lazy loading of note content
+- Efficient caching at multiple layers
+- Optimized database queries with prepared statements
+
+### Flexibility
+- Support for multiple note types
+- Extensible through scripting
+- Plugin architecture for UI widgets
+
+### Data Integrity
+- Transactional database operations
+- Revision history for all changes
+- Synchronization conflict resolution
+
+### Security
+- Per-note encryption
+- Protected sessions
+- API authentication tokens
+
+## Development Workflow
+
+1. **Setup Development Environment**
+   ```bash
+   pnpm install
+   pnpm run server:start
+   ```
+
+2. **Make Changes**
+   - Backend changes in `apps/server/src/`
+   - Frontend changes in `apps/client/src/`
+   - Shared code in `packages/`
+
+3. **Test Your Changes**
+   ```bash
+   pnpm test:all
+   pnpm nx run <project>:lint
+   ```
+
+4. **Build for Production**
+   ```bash
+   pnpm nx build server
+   pnpm nx build client
+   ```
+
+## Further Reading
+
+- [Development Environment Setup](../Environment%20Setup.md)
+- [Adding a New Note Type](../Development%20and%20architecture/Adding%20a%20new%20note%20type/First%20steps.md)
+- [Database Schema](../Development%20and%20architecture/Database/notes.md)
+- [Script API Documentation](../../Script%20API/)