Thread safety in design in LLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does thread safety mean in system design?

Thread safety means that a piece of code or design works correctly when multiple threads access it at the same time without causing errors or unexpected behavior.

beginner

Name one common problem caused by lack of thread safety.

Race conditions, where two or more threads try to change shared data at the same time, causing wrong or unpredictable results.

intermediate

What is a mutex and how does it help with thread safety?

A mutex is a lock that allows only one thread to access a resource at a time, preventing conflicts and ensuring thread safety.

intermediate

Explain immutable objects and their role in thread safety.

Immutable objects cannot be changed after creation, so multiple threads can read them safely without locks, making design simpler and safer.

advanced

What is the difference between concurrent and parallel execution in thread safety context?

Concurrent means multiple threads make progress by switching time slices, while parallel means threads run at the same time on different processors. Both need thread safety to avoid conflicts.

Which of the following best describes a race condition?

A A thread running alone without interruption

B Multiple threads accessing shared data without proper synchronization

C A thread waiting for a lock to be released

D Using immutable objects in design

Race condition happens when multiple threads access shared data simultaneously without synchronization, causing errors.

What does a mutex do in thread-safe design?

A Allows multiple threads to write data simultaneously

B Schedules threads to run in parallel

C Makes objects immutable

D Prevents multiple threads from accessing a resource at the same time

A mutex locks a resource so only one thread can access it at a time, ensuring thread safety.

Why are immutable objects considered thread-safe?

A Because they can be changed by any thread anytime

B Because they use locks internally

C Because they never change after creation, so no conflicts occur

D Because they run on a single thread

Immutable objects do not change, so multiple threads can read them safely without synchronization.

Which technique is NOT typically used to achieve thread safety?

A Ignoring shared data access

B Making objects immutable

C Using locks or mutexes

D Using atomic operations

Ignoring shared data access can cause race conditions and is not a thread safety technique.

What is the main goal of thread-safe design?

A To prevent errors when multiple threads access shared resources

B To make code run faster by using more threads

C To avoid using threads altogether

D To allow threads to share memory without restrictions

Thread-safe design ensures correct behavior when multiple threads access shared resources.

Describe what thread safety means and why it is important in system design.

Think about what happens when many people try to use the same tool at once.

List and explain at least three techniques to achieve thread safety in a design.

Consider how to control access or avoid conflicts.