Event-Driven
Event-Driven Patterns
| Pattern | Description |
|---|---|
| Event Notification | Tell what happened |
| Event-Carried State | Carry data in event |
| Event Sourcing | Store all state changes |
| CQRS | Separate read/write models |
Event Sourcing
Instead of: UPDATE product SET price = 150
Do: Store event: { type: "PriceChanged", from: 100, to: 150 }
Replay events to get current state
Key Points
- Understanding Event-Driven Architecture is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Architecture Patterns
Patterns
- Layered: Traditional
- Microservices: Distributed
- Event-Driven: Async
- Serverless: FaaS
Principles
- Single Responsibility
- loose coupling
- High cohesion
- Separation of concerns
Best Practices
- Document decisions
- Use ADRs
- Consider trade-offs
- Design for change
Key Points
- Understanding Event-Driven Architecture is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Practice Problems
Design and implement a solution for Event-Driven Architecture in a backend system. Consider scalability, error handling, and production readiness.
Solution
// Event-Driven Architecture implementation
// Key aspects: validation, error handling, logging, testing
public class EventDrivenArchitecture {
// Production-ready implementation
}Identify and handle edge cases for Event-Driven Architecture. What happens under high load, with invalid input, or during failures?
Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotencyWrite a testing strategy for Event-Driven Architecture. Include unit tests, integration tests, and performance tests.
Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injectionQuiz
1. Event sourcing stores?
2. CQRS separates?
3. What is the primary purpose of Event-Driven Architecture?
4. What is a common mistake when implementing Event-Driven Architecture?
Flashcards
Question
Event sourcing?
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Answer
Store all state changes as events
Question
CQRS?
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Answer
Separate read and write models
Question
What is Event-Driven Architecture?
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Answer
Event-Driven Architecture is a key concept in backend development.
Question
When to use Event-Driven Architecture?
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Answer
Use Event-Driven Architecture when building production systems that require reliability, scalability, and maintainability.
Question
Event-Driven Architecture best practices
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Answer
Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.
Revision Notes
Key Takeaways
- 1.Event-driven: respond to events
- 2.Event sourcing: store all changes
- 3.CQRS: separate read/write
- 4.Enables loose coupling and audit trail
Interview Tips
- •Know event-driven patterns
- •Explain event sourcing
Cheat Sheet
Event-Driven
- Event Notification: what happened
- Event Sourcing: store all changes
- CQRS: separate read/write models
- Benefits: loose coupling, audit trail