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advanced Phase · Caching

Write-Behind

Write to cache first, asynchronously flush to database.

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Write-Behind

Write-Behind Flow

1. Write goes to cache
2. Cache returns immediately
3. Cache asynchronously writes to DB

Tradeoffs

Aspect Benefit Risk
Write latency Very fast
DB load Reduced
Durability Data loss on crash
Consistency Eventual only

Key Points

  • Understanding Write-Behind Pattern is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Best Practices

Key Principles

  1. Follow SOLID principles
  2. Write clean, readable code
  3. Test thoroughly
  4. Document decisions
  5. Monitor in production

Implementation

  • Start simple, refactor as needed
  • Use established patterns
  • Consider trade-offs
  • Review with peers

Continuous Improvement

  • Learn from incidents
  • Update documentation
  • Share knowledge
  • Mentor others

Key Points

  • Understanding Write-Behind Pattern is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0 / 3 solved
Implement Write-Behind Pattern

Design and implement a solution for Write-Behind Pattern in a backend system. Consider scalability, error handling, and production readiness.

Solution 
// Write-Behind Pattern implementation
// Key aspects: validation, error handling, logging, testing

public class WriteBehindPattern {
    // Production-ready implementation
}
Write-Behind Pattern Edge Cases

Identify and handle edge cases for Write-Behind Pattern. 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, idempotency
Write-Behind Pattern Testing Strategy

Write a testing strategy for Write-Behind Pattern. Include unit tests, integration tests, and performance tests.

Solution 
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Write-behind writes to DB?

Question 1 options

2. Write-behind risk?

Question 2 options

3. What is a common mistake when implementing Write-Behind Pattern?

Question 3 options

Flashcards

Question

Write-behind DB write?

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Answer

Asynchronous (eventual)

Question

Write-behind risk?

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Answer

Data loss on crash before DB write

Question

Write-Behind Pattern 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. Write-behind: cache first, async DB write
  • 2. Very fast writes
  • 3. Risk: data loss on crash
  • 4. Good for non-critical data

Interview Tips

  • • Compare write-behind vs write-through
  • • Know tradeoffs

Cheat Sheet

Write-Behind

  • Cache first, async DB write
  • Very fast writes
  • Risk: data loss on crash
  • Use: non-critical data