ADR-001: Microservices Architecture
6/1/25About 2 minArchitecture Decisions RecordsADR
ADR-001: Microservices Architecture
Status
Accepted - July 2024
Context
BookWorm needs to demonstrate modern cloud-native patterns while maintaining educational value. The system must support:
- Independent development and deployment of different business capabilities
- Scalability for different service workloads
- Technology diversity for educational purposes
- Team autonomy in development practices
- Fault isolation and system resilience
The monolithic approach would be simpler but wouldn't demonstrate the complexities and benefits of distributed systems that are common in enterprise applications.
Decision
Adopt a microservices architecture with domain-driven service boundaries.
Service Boundaries
The system is decomposed into the following services based on business capabilities:
- Catalog Service: Book and author management
- Ordering Service: Purchase transactions and order management
- Basket Service: Shopping cart functionality
- Rating Service: Book reviews and ratings
- Chat Service: AI-powered book recommendations
- Notification Service: User communications
- Finance Service: Payment processing and financial transactions
Design Principles
- Domain-Driven Design: Services align with business domains
- Single Responsibility: Each service has one clear business purpose
- Data Ownership: Each service owns its data and database
- API-First: Well-defined service contracts
- Autonomous Teams: Services can be developed independently
Rationale
Why Microservices?
- Educational Value: Demonstrates modern enterprise patterns
- Scalability: Different services have different scaling requirements
- Technology Diversity: Can showcase different .NET technologies
- Team Simulation: Models real-world development scenarios
- Cloud-Native Alignment: Works well with .NET Aspire and Azure
Service Decomposition Strategy
Services were identified using:
- Business capability mapping
- Data ownership boundaries
- Team organization considerations
- Scalability requirements
- Technology demonstration needs
Consequences
Positive Outcomes
- Independent Deployment: Services can be deployed separately
- Technology Diversity: Different services can use different technologies
- Team Autonomy: Teams can work independently on services
- Fault Isolation: Failure in one service doesn't crash the entire system
- Scalability: Services can be scaled independently based on demand
- Educational Value: Demonstrates real-world enterprise patterns
Negative Outcomes
- Operational Complexity: More services to monitor and manage
- Network Latency: Inter-service communication overhead
- Distributed System Challenges:
- Data consistency across services
- Distributed transaction management
- Complex monitoring and debugging
- Testing Complexity: Integration testing becomes more complex
- Development Overhead: More infrastructure and deployment setup
Risk Mitigation
- Service Mesh: Consider implementing for complex routing and observability
- Circuit Breakers: Implement resilience patterns
- Distributed Tracing: Use OpenTelemetry for observability
- API Versioning: Implement versioning strategy early
- Documentation: Maintain clear service contracts and documentation
Alternatives Considered
Modular Monolith
- Pros: Simpler deployment, better performance, easier testing
- Cons: Less scalable, limited technology diversity, single point of failure
- Why Rejected: Doesn't demonstrate cloud-native patterns
Service-Oriented Architecture (SOA)
- Pros: Service reuse, enterprise integration patterns
- Cons: Too heavyweight, complex governance requirements
- Why Rejected: Overkill for the project scope and educational goals
Implementation Notes
- Services communicate via HTTP APIs and events
- Each service has its own database
- API Gateway provides unified entry point
- Service discovery handled by .NET Aspire
- Observability through OpenTelemetry