6. Runtime View

6.1 Important Scenarios

This section describes the dynamic behavior of BookWorm through key runtime scenarios, showing how the building blocks interact to fulfill important use cases.

6.2 Book Purchase Scenario

Complete Order Processing Flow

Key Runtime Aspects

1. Basket to Order Transition: Atomic conversion ensuring data consistency
2. Book Availability: Verification of catalog items during order processing
3. Financial Processing: Integration with finance service for transactions
4. Event-Driven Notifications: Asynchronous email and cleanup processes
5. Error Handling: Saga pattern for rollback on failures

6.3 Book Search and Discovery

AI-Enhanced Search Flow

Search Performance Optimizations

• Multi-level Caching: Redis cache for frequently searched terms
• Vector Search: AI embeddings for semantic similarity
• Hybrid Search: Combination of text and vector search
• Real-time Indexing: Immediate search index updates for new books

6.4 Real-time Chat Scenario

Customer Support Chat Flow

Chat System Features

• Real-time Messaging: SignalR for instant message delivery
• AI Triage: Automatic classification of customer inquiries
• Agent Routing: Intelligent assignment to available support agents
• Message Persistence: MongoDB for chat history storage
• Presence Indicators: Real-time user status updates

6.5 Event-Driven Architecture Flow

Cross-Service Event Processing

Event Processing Patterns

Pattern	Implementation	Purpose
Outbox Pattern	Database transaction + event publishing	Ensures reliable event publishing
Inbox Pattern	Idempotent event processing	Prevents duplicate processing
Event Sourcing	Events as source of truth	Provides audit trail and temporal queries
Saga Orchestration	Centralized workflow coordination	Manages complex business processes
Saga Choreography	Decentralized event reactions	Enables loose coupling between services

6.6 System Startup and Health Monitoring

Service Discovery and Health Checks

Observability and Monitoring

• Distributed Tracing: OpenTelemetry for request correlation across services
• Structured Logging: Serilog with correlation IDs and contextual information
• Metrics Collection: Prometheus-compatible metrics for performance monitoring
• Health Dashboards: Real-time system health visualization
• Alerting: Automated alerts for critical system issues

6.7 Error Handling and Recovery

Circuit Breaker Pattern Implementation

Resilience Strategies

Strategy	Implementation	Use Case
Retry Policies	Exponential backoff with jitter	Transient failures
Circuit Breakers	Polly library integration	Cascading failure prevention
Timeouts	Configurable per operation	Resource protection
Bulkhead Isolation	Separate thread pools	Fault isolation
Graceful Degradation	Fallback responses	Service unavailability