docs/EVENT_DRIVEN_ARCHITECTURE.md

Event-Driven Architecture Design

Date: 2025-01-27 Purpose: Design document for event-driven architecture integration Status: Design Document

---

Executive Summary

This document outlines the design for implementing event-driven architecture across the workspace, enabling cross-project communication and real-time updates.

---

Architecture Overview

Components

1. Event Bus (NATS, RabbitMQ, or Kafka)
2. Event Producers (Projects publishing events)
3. Event Consumers (Projects subscribing to events)
4. Event Schemas (Shared event definitions)
5. Event Monitoring (Observability and tracking)

---

Technology Options

Option 1: NATS (Recommended)

Pros:

• Lightweight and fast
• Simple setup
• Good for microservices
• Built-in streaming (NATS JetStream)

Cons:

• Less mature than Kafka
• Limited enterprise features

Option 2: RabbitMQ

Pros:

• Mature and stable
• Good management UI
• Flexible routing
• Good documentation

Cons:

• Higher resource usage
• More complex setup

Option 3: Apache Kafka

Pros:

• High throughput
• Durable message storage
• Excellent for event streaming
• Enterprise features

Cons:

• Complex setup
• Higher resource requirements
• Steeper learning curve

Recommendation: Start with NATS for simplicity, migrate to Kafka if needed for scale.

---

Event Schema Design

Event Structure

interface BaseEvent {
  id: string;
  type: string;
  source: string;
  timestamp: Date;
  version: string;
  data: unknown;
  metadata?: Record<string, unknown>;
}

Event Types

User Events

• user.created
• user.updated
• user.deleted
• user.authenticated

Transaction Events

• transaction.created
• transaction.completed
• transaction.failed
• transaction.cancelled

System Events

• system.health.check
• system.maintenance.start
• system.maintenance.end

---

Implementation Plan

Phase 1: Event Bus Setup (Weeks 1-2)

• Deploy NATS/RabbitMQ/Kafka
• Configure clusters
• Set up authentication
• Configure monitoring

Phase 2: Event Schemas (Weeks 3-4)

• Create shared event schemas package
• Define event types
• Create validation schemas
• Document event contracts

Phase 3: Producer Implementation (Weeks 5-6)

• Implement event producers in projects
• Add event publishing utilities
• Test event publishing
• Monitor event flow

Phase 4: Consumer Implementation (Weeks 7-8)

• Implement event consumers
• Add event handlers
• Test event processing
• Handle errors and retries

Phase 5: Monitoring (Weeks 9-10)

• Set up event monitoring
• Create dashboards
• Set up alerts
• Track event metrics

---

Event Patterns

Publish-Subscribe

• Multiple consumers per event
• Decoupled producers and consumers
• Use for notifications

Request-Reply

• Synchronous communication
• Response required
• Use for RPC-like calls

Event Sourcing

• Store all events
• Replay events for state
• Use for audit trails

---

Security

Authentication

• Use TLS for connections
• Authenticate producers/consumers
• Use service accounts

Authorization

• Topic-based permissions
• Limit producer/consumer access
• Audit event access

---

Monitoring

Metrics

• Event publish rate
• Event consumption rate
• Processing latency
• Error rates
• Queue depths

Alerts

• High error rate
• Slow processing
• Queue buildup
• Connection failures

---

Best Practices

Event Design

• Keep events small
• Use versioning
• Include correlation IDs
• Make events idempotent

Error Handling

• Retry with backoff
• Dead letter queues
• Log all errors
• Alert on failures

Performance

• Batch events when possible
• Use compression
• Monitor throughput
• Scale horizontally

---

Migration Strategy

Gradual Migration

1. Deploy event bus
2. Migrate one project as pilot
3. Add more projects gradually
4. Monitor and optimize

Coexistence

• Support both sync and async
• Gradual migration
• No breaking changes
• Rollback capability

---

Last Updated: 2025-01-27