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advanced Phase · Concurrency

Race Conditions

Detect and prevent race conditions in concurrent code.

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Race Conditions

What Is a Race Condition?

// NOT thread-safe
class Counter {
    private int count = 0;
    public void increment() {
        count++;  // read-modify-write (race condition!)
    }
}

// Thread A: reads count = 5
// Thread B: reads count = 5
// Thread A: writes count = 6
// Thread B: writes count = 6  ← Should be 7!

Prevention

Method Description
synchronized Lock method/block
AtomicInteger Atomic operations
Lock Explicit lock
ConcurrentHashMap Thread-safe map

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 Race Conditions 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 Race Conditions

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

Solution 
// Race Conditions implementation
// Key aspects: validation, error handling, logging, testing

public class RaceConditions {
    // Production-ready implementation
}
Race Conditions Edge Cases

Identify and handle edge cases for Race Conditions. 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
Race Conditions Testing Strategy

Write a testing strategy for Race Conditions. 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. Race condition occurs when?

Question 1 options

2. count++ is unsafe because?

Question 2 options

3. What is a common mistake when implementing Race Conditions?

Question 3 options

Flashcards

Question

Race condition?

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Answer

Multiple threads accessing shared data concurrently

Question

count++ unsafe?

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Answer

Read-modify-write is not atomic

Question

Race Conditions 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. Race condition: concurrent access to shared data
  • 2. count++ is read-modify-write (not atomic)
  • 3. Use synchronized, AtomicInteger, or Lock
  • 4. Always think about thread safety

Interview Tips

  • • Identify race conditions
  • • Know prevention methods

Cheat Sheet

Race Conditions

  • Concurrent access to shared data
  • count++ = read + modify + write (not atomic)
  • Fix: synchronized, AtomicInteger, Lock
  • Always check thread safety