Concurrency Concepts: Race Conditions, Idempotency, and Duplicate Prevention Quiz

Test your understanding of concurrency basics, including race conditions, idempotent processing, and techniques for avoiding duplicate work. This quiz covers key principles for writing safe and efficient concurrent code.

1. Understanding Race Conditions

   What is a race condition in a concurrent program involving two threads updating the same variable?

   1. A special data type that ensures thread safety
   2. A situation where a program crashes due to network failure
   3. An error that occurs when two threads access and modify shared data simultaneously, leading to unpredictable results
   4. A bug that occurs only in single-threaded programs

2. Preventing Duplicate Processing

   Which technique can help avoid processing the same data multiple times in a concurrent environment?

   1. Using unique identifiers to track processed items
   2. Ignoring all incoming tasks
   3. Increasing the clock speed of the CPU
   4. Saving processed items in a random list without checking

3. Idempotent Operations

   Which of the following best describes an idempotent operation?

   1. An operation that requires user confirmation each time
   2. An operation that can be applied multiple times without changing the result beyond the initial application
   3. An operation that must only be performed once to avoid errors
   4. An operation that always causes side effects

4. Example of Race Condition

   In a scenario where two concurrent processes both attempt to decrement a shared counter from 1 to 0, what problem could occur without synchronization?

   1. An out-of-memory error occurs
   2. The counter always increases
   3. One process waits forever for the other
   4. Both see the counter as 1 and set it to 0, resulting in an incorrect final value

5. Atomic Operations

   What is the primary purpose of an atomic operation in a concurrent environment?

   1. To make variables read-only
   2. To slow down the program intentionally
   3. To ensure a sequence of actions appears indivisible and cannot be interrupted
   4. To randomly shuffle data

6. Duplicate Work Scenarios

   Why is avoiding duplicate work important in concurrent systems processing messages from a shared queue?

   1. It allows multiple programs to crash together
   2. It guarantees that all messages are ignored
   3. It prevents wasted resources and ensures accurate results
   4. It ensures all messages are deleted immediately

7. Locking Mechanisms

   What role does a locking mechanism play in preventing race conditions?

   1. It makes all threads finish at the same time
   2. It encrypts shared data after every operation
   3. It allows only one thread to access critical sections at a time
   4. It disables multithreading completely

8. Idempotency in APIs

   Why is it important for an API endpoint to be idempotent when handling repeated requests?

   1. To make the API slower by default
   2. So repeated calls do not cause unintended changes or duplicate work
   3. So it randomly changes its results on each call
   4. To require more user permissions with each call

9. Recognizing a Non-Idempotent Operation

   Which of the following is an example of a non-idempotent operation in a checkout system?

   1. Checking the status of an order multiple times
   2. Charging a customer’s credit card twice when the same request is received twice
   3. Retrieving an order summary several times
   4. Getting the list of all available products

10. Duplicate Work in Distributed Systems

    In a distributed system where work items may be retried due to transient errors, what is a common strategy to prevent duplicate processing?

    1. Assume that network errors never happen
    2. Restart processing from scratch each time
    3. Assign a unique id to each work item and track completed ones before processing again
    4. Ignore the need to track work items