Microservices is an architectural style that structures an application as a collection of small, loosely coupled services. Each service is focused on doing one thing well, runs in its own process, and communicates via well-defined APIs. Independently deployable services that together form a larger application

E-commerce Microservice Architecture

1. User Service:
   • Responsibility: Manages user profiles, authentication, and authorization.
   • Functionality:
     • User registration, login, and password management.
     • Stores user data such as name, address, email, etc.
     • Generates JWT tokens for authenticated sessions.
   • Tech Stack: Node.js with JWT for authentication, MongoDB for user data storage.
2. Product Service:
   • Responsibility: Manages product catalogs and inventory.
   • Functionality:
     • Product listing, categories, and search functionality.
     • Tracks stock levels for each product.
     • Product recommendations or related products.
   • Tech Stack: Python (Flask/Django), PostgreSQL or NoSQL like MongoDB.
3. Order Service:
   • Responsibility: Manages user orders.
   • Functionality:
     • Processes new orders placed by users.
     • Tracks the status of each order (e.g., processing, shipped, delivered).
     • Handles order cancellation and returns.
   • Tech Stack: Java Spring Boot, MySQL.
4. Payment Service:
   • Responsibility: Handles all payment-related tasks.
   • Functionality:
     • Integrates with third-party payment gateways (e.g., Stripe, PayPal).
     • Processes payments and refunds.
     • Ensures secure transaction processing.
   • Tech Stack: Ruby on Rails, with external API integration to payment gateways.
5. Shipping Service:
   • Responsibility: Manages shipment and delivery.
   • Functionality:
     • Determines shipping costs based on user location.
     • Integrates with third-party couriers (e.g., FedEx, UPS).
     • Tracks shipment and delivery statuses.
   • Tech Stack: Go, Kafka for message queuing and real-time updates.
6. Notification Service:
   • Responsibility: Sends notifications to users.
   • Functionality:
     • Sends order confirmations, shipping updates, and promotional emails.
     • Handles both email and SMS notifications.
     • Supports WebSocket for real-time notifications.
   • Tech Stack: Node.js with WebSocket, Firebase for push notifications.
7. Review and Rating Service:
   • Responsibility: Handles customer reviews and ratings of products.
   • Functionality:
     • Allows users to submit product reviews.
     • Manages ratings, ensuring only valid users can leave reviews.
     • Displays aggregated ratings for products.
   • Tech Stack: Express.js, Elasticsearch for full-text search functionality.

Interaction Between Microservices

• API Gateway: All user requests first go through an API Gateway. It routes requests to the appropriate microservice, handles cross-cutting concerns like rate limiting, security (e.g., token validation), and caching.
• Message Broker (e.g., RabbitMQ or Kafka): Services like the Order Service, Payment Service, and Shipping Service can communicate asynchronously using a message broker. For example, once an order is placed, the Order Service sends an event message to the Payment Service to process payment, and another message to the Shipping Service to arrange delivery.
• Service Discovery (e.g., Consul): Keeps track of all the microservices, enabling dynamic service discovery for communication.
• Database per Service: Each service has its own database to ensure loose coupling. For example:
  • User Service might use MongoDB.
  • Order Service might use MySQL.
  • Product Service might use PostgreSQL.
• CI/CD Pipeline: Continuous integration/continuous delivery pipelines are used for deploying and scaling each microservice independently.

Example Workflow:

1. User makes an order:
   • The User Service authenticates the user.
   • The Order Service creates a new order.
   • The Payment Service processes the payment.
   • The Shipping Service calculates delivery options and arranges shipment.
   • The Notification Service sends an order confirmation email to the user.
2. Shipping Updates:
   • The Shipping Service tracks the delivery.
   • The Notification Service sends updates to the user about the shipping status.

This structure ensures scalability, flexibility in choosing technologies, and ease of maintenance as each service can be developed, tested, and deployed independently.

Microservices vs. Monolithic Architecture