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docs/architecture.md

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+To build a solid **e-commerce backend using Spring Boot**, you need to design it around core business domains, security, scalability, and integrations.
+
+Here’s a structured roadmap 👇
+
+---
+
+# 1️⃣ Core Functional Modules
+
+## 🧑‍💼 1. User & Authentication Module
+
+* User registration & login
+* Role-based access (ADMIN, CUSTOMER, SELLER)
+* JWT or OAuth2 authentication
+* Password encryption (BCrypt)
+* Email verification
+* Forgot/reset password
+
+**Technologies**
+
+* Spring Security
+* JWT
+* OAuth2 (optional)
+* BCryptPasswordEncoder
+
+---
+
+# 2️⃣ Recommended Architecture
+
+### 🔹 Layered Architecture
+
+* Controller layer (REST APIs)
+* Service layer (Business logic)
+* Repository layer (Data access)
+* DTO & Mapper layer (MapStruct recommended)
+
+### 🔹 Database
+
+* PostgreSQL / MySQL
+* Redis (caching, cart)
+* Elasticsearch (for search, optional)
+
+---
+
+# 3️⃣ Important Technical Features
+
+## 🔐 Security
+
+* Spring Security
+* JWT authentication
+* CSRF protection
+* CORS config
+* Rate limiting
+* Input validation
+
+---
+
+## ⚡ Performance & Scalability
+
+* Caching (Redis)
+* Pagination
+* Indexing DB columns
+* Async processing
+* Connection pooling (HikariCP)
+
+---
+
+## 📡 API Design
+
+* RESTful endpoints
+* Proper HTTP status codes
+* Exception handling (GlobalExceptionHandler)
+* Swagger / OpenAPI documentation
+
+---
+
+## 🧾 Logging & Monitoring
+
+* Logback
+* ELK stack
+* Actuator
+* Prometheus & Grafana
+
+---
+
+# 4️⃣ Advanced / Production-Level Features
+
+* Microservices architecture
+* API Gateway
+* Circuit breaker (Resilience4j)
+* Kafka for order events
+* Docker + Kubernetes
+* CI/CD pipeline
+* Cloud deployment (AWS/GCP/Azure)
+
+---
+
+# 5️⃣ Suggested Database Entities
+
+Basic Entities:
+
+* User
+* Role
+
+---
+
+# 6️⃣ Tools & Dependencies
+
+Spring Boot Starters:
+
+* spring-boot-starter-web
+* spring-boot-starter-data-jpa
+* spring-boot-starter-security
+* spring-boot-starter-validation
+* spring-boot-starter-actuator
+
+Other:
+
+* Lombok
+* MapStruct
+* Flyway or Liquibase
+* Redis
+* Docker
+
+---
+
+# 7️⃣ Typical Development Roadmap
+
+1. Setup project
+2. Configure DB
+3. Implement User & Security
+8. Add caching
+9. Add logging & monitoring
+10. Deploy
+
+
+        ┌───────────────┐
+        │   Keycloak    │
+        └──┬─────────┬──┘
+   PKCE ──┘         └── OIDC code flow
+   (mobile)         (BFF callback)
+        │             │
+   ┌────▼───┐     ┌───▼────┐
+   │ Mobile │     │  BFF   │  ← Spring app, holds session
+   └────┬───┘     └───┬────┘
+        │ Bearer      │ Bearer (server-attached)
+        └──────┬──────┘
+               ▼
+        ┌─────────────┐
+        │ Resource API│  ← validates JWT via JWKS
+        └─────────────┘