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Sends 2 messages

This service sends messages to downstream consumers

Receives 4 messages

This service receives messages from other services

Overview

The Rating Service represents a distinct bounded context within the BookWorm ecosystem, responsible for managing user feedback and ratings for books. As a core domain service, it implements Domain-Driven Design principles to maintain a clean separation of concerns while providing critical functionality for the user experience.

Key Responsibilities

• Collecting and storing user ratings and reviews
• Calculating aggregate rating metrics for books
• Validating feedback content against business rules
• Publishing domain events when feedback changes

Domain Events

The service emits domain events such as FeedbackCreatedEvent and FeedbackDeletedEvent to notify other bounded contexts about changes in the rating domain. These events enable loose coupling between services while maintaining data consistency.

Integration Points

Rating Service integrates with:

• Catalog Service: Updates book rating information
• Notification Service: Triggers notifications for review responses

Implementation Details

The service follows the CQRS pattern with separate command and query models, enabling optimized read and write operations. The repository pattern is used for data access, ensuring persistence concerns remain separated from domain logic.

Core Features

Feature	Description
Add Feedback	Allows users to submit feedback and ratings for books, storing them in the database.
Delete Feedback	Supports the removal of user feedback, updating the book’s rating metrics accordingly.
Get Feedbacks	Provides an API endpoint to retrieve feedback for a specific book or user.

Architecture diagram

Technical Architecture

The Rating Service is built on a modern, cloud-native architecture following these key design principles:

Command Query Responsibility Segregation (CQRS)

The service implements CQRS pattern with:

• Command Stack: Handles write operations through commands like CreateFeedbackCommand and DeleteFeedbackCommand
• Query Stack: Manages read operations with queries like ListFeedbackQuery
• MediatR Pipeline: Processes commands and queries with cross-cutting concerns:
  • Validation behavior
  • Activity tracking for observability
  • Logging behavior

Event-Driven Architecture

The service publishes domain events that are transformed into integration events for cross-service communication:

• Domain Events: FeedbackCreatedEvent, FeedbackDeletedEvent
• Integration Events: FeedbackCreatedIntegrationEvent, FeedbackDeletedIntegrationEvent
• Event Bus: Implemented with MassTransit for reliable message delivery
• Inbox/Outbox Pattern: Ensures at-least-once delivery semantics

Infrastructure

This service is built using C# and .NET Core, leveraging Entity Framework Core for data access and Azure Cosmos Database for persistence. The service is containerized using Docker and deployed to Azure Kubernetes Service (AKS) for scalability and reliability.