Table of Contents
Codebase Architecture: Designing for Scale, Modularity, and Sanity¶
A Practical Guide to Structuring React + FastAPI Projects in the Age of AI¶
Contents¶
📖 Preface¶
Part I – Foundations¶
Chapter 1: Introduction
1.1 What this book solves?
1.2 Who this book is for
Chapter 2: Why Folder Structure Matters
2.1 Anatomy of growing software chaos
2.2 Real-world symptoms of bad structure
2.3 The role of architecture in scale and collaboration
Chapter 3: Modularity vs. Scalability
3.1 Definitions and core differences
3.2 Why most projects need both
3.3 Thinking in layers vs. features
Chapter 4: How Structure Impacts Software Quality
4.1 Maintainability
4.2 Testability
4.3 Developer onboarding
4.4 Refactoring ease
Chapter 5: Core Principles of Architecture
5.1 Separation of Concerns
5.2 High Cohesion, Low Coupling
5.3 DRY and Reusability
5.4 Convention over Configuration
5.5 Structure as API for teams
Chapter 6: Understanding the Stack
6.1 Overview of React + Vite (Frontend)
6.2 Overview of FastAPI (Backend)
6.3 How they communicate (REST, WebSockets, Streaming)
6.4 Shared challenges: auth, state sync, rate limiting, API versioning
Part II – Modularity¶
Chapter 7: Modular Architecture Overview
7.1 What is modular structure?
7.2 MWhen to use it
7.3 Benefits vs. drawbacks
Chapter 8: Modular Folder Structure for React + Vite
8.1 Feature-first organization
8.2 Example folder breakdown
8.3 Managing component isolation
8.4 Organizing hooks, services, and utils within modules
8.5 Naming conventions for modular files
8.6 Avoiding shared state bleed
Chapter 9: Modular Folder Structure for FastAPI
9.1 Feature-centric backend design
9.2 Organizing routes, schemas, services
9.3 Keeping shared logic clean (e.g., OCR, GPT clients, DB connectors)
9.4 Handling circular imports
9.5 Structuring testable service layers
9.6 Dependency injection and inversion
Chapter 10: Testing in Modular Projects
10.1 Writing tests per module
10.2 Shared mock strategies
10.3 Organizing test folders and fixtures
10.4 Keeping modules independently testable
Part III – Scalability¶
Chapter 11: Scalable Architecture Overview
11.1 When modular is not enough
11.2 Symptoms of scale pressure
11.3 Layered design thinking
Chapter 12: Scalable Folder Structure for React + Vite)
12.1 Layer-first approach: /api, /services, /hooks, /components
12.2 Managing cross-feature logic and global state
12.3 Shared UI systems and design tokens
12.4 Component libraries and scalable styling
12.5 Supporting multiple teams on the same codebase
Chapter 13: Scalable Folder Structure for FastAPI
13.1 Layered backend: /api, /services, /schemas, /core, /infra
13.2 Clean separation of routers, models, and business logic
13.3 Supporting background jobs (e.g., Celery, FastAPI tasks)
13.4 Auth, permissions, and role-based modules
13.5 Versioned routing and scalable endpoints
13.6 Repository pattern for data access
13.7 Handling vector DBs and external APIs gracefully
Chapter 14: Deploying and Scaling React + FastAPI Projects
14.1 Folder structure impact on CI/CD pipelines
14.2 Docker best practices for structure
14.3 Managing environment variables and secrets
14.4 Static files and public assets
14.5 Horizontal vs. vertical scaling
14.6 Infra as code (IaC) tips for growth
Part IV – Hybrid and Advanced Techniques¶
Chapter 15: Hybrid Folder Structures
15.1 What hybrid means (modular + scalable)
15.2 Use cases for hybridization
15.3 Evolving modular apps to scalable ones
15.4 Gradual migration strategies
15.5 Refactor patterns and heuristics
Chapter 16: Monorepos and Shared Logic
16.1 When to use a monorepo
16.2 Structuring React + FastAPI in one codebase
16.3 Sharing types, schemas, and validations
16.4 Using pnpm workspaces, Turborepo, or Nx
16.5 Versioning strategies for shared logic
Chapter 17: Organizing Assets, Tests, and Configuration
17.1 Best practices for /assets, /env, /docs, and /configs
17.2 Feature-based vs. centralized testing
17.3 Managing mock data and API fakes
17.4 Global configs vs. per-feature config files
17.5 Linting, formatting, and pre-commit structuring
Chapter 18: Migration Playbook
18.1 From flat → modular → scalable
18.2 Folder audit checklist
18.3 Common mistakes and how to resolve them
18.4 Refactor-safe conventions
Part V – Case Studies and Templates¶
Chapter 19: Case Study: Smart Receipt/Invoice Analyzer
19.1 OCR-first modular architecture
19.2 GPT pipeline integration
19.3 Frontend dynamic table + backend processing
19.4 How modular evolved into hybrid
Chapter 20: Case Study: Document Intelligence Chatbot
20.1 Fully scalable design
20.2 Embeddings and vector DBs
20.3 Chat UI, streaming, RAG pipeline
20.4 React frontend folder → FastAPI backend folder
Chapter21: Case Study: AI-Powered Mockup-to-Code Tool
21.1 GPT-driven frontend generator
21.2 Image parsing modules
21.3 Event and layout-driven architecture
Chapter 22: Complete Starter Templates
22.1 React + FastAPI Modular Template
22.2 React + FastAPI Scalable Template
22.3 React + FastAPI Hybrid AI App Template
22.4 Folder walk-throughs and clone instructions
Appendices¶
A. Glossary of Terms
B. Tools and Libraries Reference
C. Recommended Folder Structures (Cheat Sheets)
D. Formatter, Linter, and Dev Config Tips
E. Further Reading and Resources
F. Migration Checklist & Structure Audit Guide