Building a Fault-Tolerant Order Processing System
Design a system that processes orders reliably even when components fail.
Problem Statement
Design a system that processes orders reliably even when components fail.
Context: E-commerce platform handling 10,000+ orders/day with 99.9% uptime requirement.
Architecture Overview
The system uses a saga pattern with event sourcing to ensure reliable order processing
Key Decisions & Trade-offs
Analysis of architectural decisions and their implications
Event Sourcing
Pros
Full audit trail, temporal queries
Cons
Eventual consistency, complexity
Why chosen: Compliance requirements
Saga Pattern
Pros
Handles distributed transactions
Cons
Complex rollback logic
Why chosen: Business requirement for atomicity
Implementation Guide
Step-by-step guide to implement this architecture
1. Event Store Setup
Set up the event store to capture all order state changes
interface OrderEvent {
id: string;
orderId: string;
type: 'OrderCreated' | 'PaymentReserved' | 'InventoryReserved';
data: any;
timestamp: Date;
version: number;
}2. Saga Orchestration
Implement the saga pattern for distributed transaction management
class OrderSaga {
async execute(order: Order): Promise<Result> {
try {
await this.reservePayment(order);
await this.reserveInventory(order);
await this.confirmOrder(order);
return Result.success();
} catch (error) {
await this.compensate(order);
return Result.failure(error);
}
}
}Operational Considerations
Monitoring, alerting, and failure handling strategies
SLOs & Monitoring
- • Latency: P95 < 500ms for order creation
- • Availability: 99.9% uptime
- • Error Rate: < 0.1% for critical operations
Failure Modes
- • Payment Service Down: Circuit breaker to fallback
- • Inventory Service Down: Queue orders for later processing
- • Event Store Down: Store events locally, sync when available
Results & Metrics
Before and after comparison of system performance
Before Implementation
- • Order success rate: 85%
- • Average processing time: 2.5s
- • Manual reconciliation: 3 hours/day
After Implementation
- • Order success rate: 99.2%
- • Average processing time: 450ms
- • Manual reconciliation: 15 minutes/day