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intermediate Phase · Database Integration

Primary Keys

Define and generate primary keys for JPA entities.

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Primary Key Strategies

ID Generation Strategies

@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;  // Auto-increment

@Id @GeneratedValue(strategy = GenerationType.UUID)
private UUID id;   // UUID

@Id
private String id;  // Assigned

Strategy Comparison

Strategy Pros Cons
IDENTITY Simple DB-specific
SEQUENCE Standard Not MySQL
UUID Globally unique Larger storage
ASSIGNED Business key Must ensure uniqueness

Key Points

  • Understanding Primary Keys 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 Primary Keys 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 Primary Keys

Design and implement a solution for Primary Keys in a backend system. Consider scalability, error handling, and production readiness.

Solution 
// Primary Keys implementation
// Key aspects: validation, error handling, logging, testing

public class PrimaryKeys {
    // Production-ready implementation
}
Primary Keys Edge Cases

Identify and handle edge cases for Primary Keys. 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
Primary Keys Testing Strategy

Write a testing strategy for Primary Keys. 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. Best ID strategy for distributed systems?

Question 1 options

2. IDENTITY uses what?

Question 2 options

3. What is a common mistake when implementing Primary Keys?

Question 3 options

Flashcards

Question

Best for distributed?

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Answer

UUID - globally unique

Question

IDENTITY?

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Answer

Auto-increment columns

Question

Primary Keys 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. IDENTITY: auto-increment (MySQL)
  • 2. SEQUENCE: DB sequences (PostgreSQL)
  • 3. UUID: globally unique, distributed-friendly

Interview Tips

  • • Choose ID strategy
  • • Know UUID vs auto-increment

Cheat Sheet

Primary Keys

  • IDENTITY: auto-increment
  • SEQUENCE: DB sequences
  • UUID: globally unique
  • ASSIGNED: business key