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Backend Architecture Deep Dive

The FitNexa backend is a distributed system designed for scalability, isolation, and observability.

🛠️ Tech Stack​

  • Runtime: Node.js (TypeScript)
  • Framework: Express.js
  • Database: PostgreSQL with Prisma ORM
  • Messaging: RabbitMQ (amqplib)
  • Caching: Redis (ioredis)
  • Logging: Winston + MongoDB
  • Shared Library: @fitnexa/shared (Custom internal package)

📦 Service Design Patterns​

1. Database per Service​

Each microservice owns its own database schema (e.g., fitnexa_identity, fitnexa_gym). This ensures that a schema change in one service never breaks another.

2. API Gateway (Gatekeeper)​

The Gateway (Port 3000) acts as the single entry point. It handles:

  • Routing: Mapping client requests to downstream services.
  • Health Monitoring: Aggregating readiness/liveness of all services.
  • Cross-Component Auth: (Future) Centralized token validation.

3. Shared Core Library (@fitnexa/shared)​

To avoid code duplication, common logic is moved to a local shared package. It supports sub-path exports for granular imports:

  • @fitnexa/shared/types: Shared interfaces for users, gyms, and events.
  • @fitnexa/shared/api: Platform-agnostic API clients.
  • @fitnexa/shared/logger: Environment-aware logging (Console in browser, Winston in Node).
  • @fitnexa/shared/middleware: Error handling, correlation IDs, performance monitoring.
  • @fitnexa/shared/server: Backend-only entry: ConfigManager, createBaseService, bootstrap, and Node-only config. All microservices import from @fitnexa/shared/server (via path mapping in tsconfig.json) so they do not pull browser-only code. See Shared Package for full export reference.

📡 Communication Patterns​

Synchronous (REST)​

Used for immediate requests where a response is required (e.g., Login, Fetching Workouts).

Asynchronous (Events)​

Used for non-blocking operations to improve resilience and performance:

  • Logging: Services publish logs to the logs exchange in RabbitMQ.
  • Cross-Service Sync: (e.g., When a user is deleted in Identity, notify other services).

Real-time (WebSockets)​

Handled via socket.io in specific services like Messaging and Squad Service for instant notifications and chat.

🔗 Related Links​