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Create Order Scenario

The Create Order scenario represents the core business process of BookWorm, handling the complete journey from customer checkout to order fulfillment. This flow implements the Saga pattern to ensure data consistency across distributed services.

Overview​

This end-to-end flow orchestrates multiple microservices to process customer orders, focusing on proper inventory management, basket cleanup, and customer communication throughout the order lifecycle.

🎯 Business Context​

Objectives​

  1. Seamless Checkout: Minimize friction in the purchase process
  2. Inventory Accuracy: Prevent overselling through proper reservation
  3. Data Consistency: Ensure proper basket cleanup after order creation
  4. Customer Communication: Keep customers informed throughout

Success Criteria​

  • ✅ Order creation within 5 seconds
  • ✅ 99.9% success rate for valid orders
  • ✅ Proper basket cleanup after order completion
  • ✅ Confirmation notification within 1 minute

🔄 Order Processing Flow​

The following sequence diagram illustrates the complete order creation and processing flow:

📋 Detailed Process Steps​

1. Order Initiation​

Actions:

  • User submits order with selected items
  • System validates order data and business rules
  • CreateOrderCommand is generated and sent to Ordering Service

2. Order Orchestration​

Actions:

  • Finance Service receives checkout event
  • Coordinates the order processing workflow
  • PlaceOrderCommand is sent to Basket Service

3. Basket Management​

Actions:

  • Basket Service reserves ordered items
  • Attempts to delete user's basket after order confirmation
  • Publishes appropriate event based on outcome

4. Order Completion & Compensation​

Actions:

  • Success Path: Order confirmed, notification sent
  • Failure Path: Order rolled back, basket restored

📋 Business Rules​

Order Validation Rules​

RuleDescriptionAction on Violation
Minimum Order ValueOrders must be >= $10Reject with error message
Maximum ItemsMax 50 unique items per orderSplit into multiple orders
Stock AvailabilityAll items must be in stockSuggest alternatives
Shipping AddressMust be deliverable regionShow supported regions

Compensation Rules​

When failures occur, the system automatically compensates:

  1. Basket Clear Failed:

    • Cancel order record
    • Restore basket contents
    • Alert support team for investigation

  2. Notification Failed:

    • Retry with exponential backoff
    • Log for manual follow-up
    • Order processing still completes successfully

🏗️ Architecture Patterns​

Saga Pattern Implementation​

The order flow implements the Choreography-based Saga pattern:

  • Event-Driven: Services communicate through domain events
  • Autonomous: Each service manages its own compensation logic
  • Resilient: Automatic retry and rollback mechanisms
  • Observable: Complete audit trail of all events

📈 SLA Requirements​

Service Level Agreement​

ComponentAvailabilityResponse TimeError Rate
API Gateway99.99%< 50ms< 0.01%
Ordering Service99.9%< 200ms< 0.1%
Finance Service99.9%< 200ms< 0.1%
Basket Service99.9%< 100ms< 0.1%
Notification Service99.5%< 1000ms< 0.5%
Overall Flow99.9%< 5s< 0.1%

🛡️ Security Considerations​

Data Protection​

  • Encryption at Rest: Order data encrypted in database
  • Access Control: Role-based access to order information
  • Data Retention: Compliance with data retention policies
  • GDPR Compliance: Customer data protection rights

🔍 Monitoring & Observability​

Key Metrics​

  • Order Success Rate: Percentage of successfully completed orders
  • Average Processing Time: Time from checkout to confirmation
  • Basket Cleanup Rate: Success rate of basket deletion after orders
  • Compensation Events: Frequency of rollback scenarios
  • Customer Satisfaction: Order fulfillment ratings

Alerting Thresholds​

  • Order Success Rate < 99%: Critical alert
  • Processing Time > 10s: Warning alert
  • Basket Cleanup Failures > 1%: Investigation required
  • Multiple Compensations: Potential system issue