How quanghoatb/book-management works
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1. Identify the project type and purpose
- This is a NestJS‑based monorepo containing two backend microservices (auth‑service and book‑service), a simple gateway for Swagger integration, and a shared library (auth‑common).
- Its purpose is to offer authentication and book‑management APIs in a microservices architecture, with common authentication utilities factored out into a shared lib.
2. Analyze the file structure
- Top level:
• apps/ : contains auth‑service and book‑service NestJS applications
• gateway/ : holds a minimal Swagger gateway project
• libs/auth‑common/ : shared authentication utilities (decorators, interfaces, guards)
• pnpm workspace and TS configs for monorepo management
- Each service has its own src/ folder with modules (auth, users, books), controllers, services, entities, DTOs, and main.ts entry point.
- No UI folder—this is a purely server‐side system.
- No explicit database config files here, but presence of “*.entity.ts” implies each service uses an ORM (likely TypeORM) and a backing database.
3. Examine the README
- It’s the default NestJS starter readme; no custom diagrams or architecture details.
- It confirms a multi‐app Nest workspace using pnpm.
4. How to create the system design diagram
a. Main components
- Client (e.g., mobile app, web frontend)
- API Gateway (gateway/swagger‑gateway)
- Auth Service (apps/auth‑service)
- Book Service (apps/book‑service)
- Shared Auth Library (libs/auth‑common)
- Databases (one per service or a shared database, depending on configuration)
b. Relationships and interactions
- Client → HTTP/HTTPS → Gateway
- Gateway → routes to Auth Service and Book Service via HTTP
- Auth Service uses its Users module to manage user records in its database
- Book Service verifies JWT (via libs/auth‑common) and CRUD‑manages Book entities in its DB
- Both services import and use libs/auth‑common for consistent JWT strategy, guards, decorators
c. Architectural patterns and design principles
- Microservices pattern: each domain (auth, books) is isolated in its own NestJS app
- Shared‑lib pattern: common code extracted to libs/auth‑common to avoid duplication
- Modular NestJS structure: each feature is a Nest module with controllers, services, DTOs, entities
- API Gateway pattern: a simple entry point that aggregates Swagger docs and routes calls
d. Key technologies and frameworks
- NestJS (framework for each service)
- TypeScript (language)
- pnpm workspaces (monorepo management)
- TypeORM or other ORM for entities
- JWT for authentication (passport‑jwt under the hood)
- Swagger (for API documentation via the gateway)
5. Tailoring the diagram to this project
- Emphasize separation: clearly show each NestJS app as its own bounded context
- Show the shared library as a separate artifact that both services depend on
- Illustrate the gateway’s role as an API facade (even if it’s only for Swagger, it can be extended)
- Do not include frontend UIs—focus on backend services and data flows
6. Elements to include in the diagram
- Clear labeled boxes or containers for: Client, Gateway, Auth Service, Book Service, Shared Auth Lib, Databases
- Directional arrows:
• Client → Gateway (API request)
• Gateway → Auth Service / Book Service
• Services → their respective databases
• Services → Shared Auth Lib (dependency link)
- Color coding or shapes to distinguish component types:
• One color for API gateway
• One for microservices
• One for shared libraries
• Cylinder icons for databases
- Annotation of protocols (HTTP, JWT) on the arrows
7. Final guidelines for the principal software engineer
- Start by sketching each service as an isolated container, placed side by side
- Above them, place the gateway container; below, place each service’s database cylinder
- Offset the shared auth library to the side, with dashed dependency arrows into auth‑service and book‑service
- Label each arrow with the communication mechanism (e.g., “HTTP + JSON”, “JWT validation”)
- Use consistent colors or shapes so a reader can instantly tell “service vs. data store vs. library”
- Ensure every module, external dependency, and data flow is captured—don’t omit the shared lib or the gateway
- Review the file tree and README to verify you’ve represented all top‑level components
By following these steps, you will produce a detailed, accurate system design diagram that reflects this NestJS microservices monorepo, shows clear separation of concerns, and documents the relationships and technologies in use.
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