E-Commerce

A distributed e-commerce backend made of Spring Boot microservices. It uses PostgreSQL per service, Redis for caching and auth token handling, Apache Kafka for asynchronous order and payment flows, and Zipkin-compatible tracing. Everything needed for local development is orchestrated with Docker Compose.

Architecture

Traffic enters through the API Gateway (:8080), which routes /api/** requests to the appropriate service by path. Each service owns its PostgreSQL database (created on first Postgres startup). Order placement publishes an order-placed event; the payment service consumes it, records a payment, and publishes payment-processed; the order service updates order status from that topic, and the notification service persists user-facing notifications from both topics.

flowchart LR
  Client --> Gateway
  Gateway --> UserSvc[User Service]
  Gateway --> ProductSvc[Product Service]
  Gateway --> OrderSvc[Order Service]
  Gateway --> PaymentSvc[Payment Service]
  Gateway --> NotifSvc[Notification Service]
  OrderSvc --> Kafka[Kafka]
  PaymentSvc --> Kafka
  NotifSvc --> Kafka
  OrderSvc --> ProductSvc
  UserSvc --> PG[(PostgreSQL)]
  ProductSvc --> PG
  OrderSvc --> PG
  PaymentSvc --> PG
  NotifSvc --> PG
  UserSvc --> Redis[(Redis)]
  ProductSvc --> Redis

Tech stack

Area	Technology
Language & runtime	Java 17
Framework	Spring Boot 3.2 (Web, Data JPA, Security, Kafka, Actuator, Validation)
API gateway	Spring Cloud Gateway (WebFlux)
Databases	PostgreSQL 15 (one database per service via init script)
Migrations	Flyway
Messaging	Apache Kafka (Confluent 7.5 images) + Zookeeper
Cache	Redis 7
API docs	springdoc-openapi (Swagger UI on each REST service)