2.2 Backend

Goal: Provide a secure, scalable, and extensible API layer that powers user authentication, data operations, trading logic, and administrative features.

1. Node.js/Express

• Structure:

• Modular routes (e.g., /api/users, /api/trades, /api/channels).

• Controllers for business logic (e.g., userController, tradeController).

• Middleware (auth, rate-limiting, error handling).

• Authentication:

• JWT tokens for stateless auth.

• OAuth2 or custom token-based flows for external wallet integrations.

• Data Handling:

• Sequelize ORM with PostgreSQL for relational data.

• Validation using libraries like Joi or express-validator.

• Services Layer (optional):

• Encapsulate third-party API calls (crypto market data, wallet verification).

• Keep controllers lean, focusing on request handling.

• Scalability:

• Horizontal scaling (Node Cluster or container orchestration) behind a load balancer.

• Redis caching for frequently accessed data (e.g., trending coins, chat presence).

2. Microservices vs. Monolith

• Phase 1: Start with a well-structured monolith to reduce complexity.

• Future: Evolve into microservices (e.g., Chat Service, Trade Service) as user load and feature demands grow.

3. API Documentation

• Swagger (OpenAPI) or Postman collections for easy reference + testing.