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Event-Driven Architecture
Definition
Event-Driven Architecture (EDA) is a design pattern where components communicate by producing and consuming events. An event represents a significant change in state. Services react to events asynchronously, enabling loose coupling and scalability.
When to Use It
- Building real-time data processing systems
- You need loose coupling between services
- Handling high-volume, asynchronous workflows
- Implementing complex business processes
- Building reactive and responsive systems
- Integration across multiple systems
Pros & Cons
✓ Pros
- Loose coupling between services
- Highly scalable and elastic
- Easy to add new consumers
- Better fault tolerance
- Asynchronous processing
- Real-time event processing
✗ Cons
- Increased system complexity
- Difficult to track event flows
- Eventual consistency challenges
- Debugging is more complex
- Requires event schema management
- Potential for duplicate events
Architecture Diagram
Event Producers
===============
┌──────────┐ ┌──────────┐ ┌──────────┐
│ User │ │ Payment │ │ Inventory│
│ Service │ │ Service │ │ Service │
└────┬─────┘ └────┬─────┘ └────┬─────┘
│ │ │
│ Publish │ Publish │ Publish
▼ ▼ ▼
┌─────────────────────────────────────┐
│ Event Bus / Message Broker │
│ (Kafka, EventBridge) │
│ │
│ Topics: │
│ • user.created │
│ • payment.completed │
│ • inventory.updated │
└──────┬──────────┬──────────┬────────┘
│ │ │
Subscribe│ Subscribe│ Subscribe│
▼ ▼ ▼
┌──────────┐ ┌──────────┐ ┌──────────┐
│ Email │ │Analytics │ │ Audit │
│ Service │ │ Service │ │ Service │
└──────────┘ └──────────┘ └──────────┘
Event Consumers
===============
Flow:
1. Producers publish events to the event bus
2. Event bus routes events to subscribed consumers
3. Consumers process events asynchronously
4. Multiple consumers can react to same event
5. New consumers can be added without changes