15 Top Concurrency Interview Questions and Answers (2024)

Blog / 15 Top Concurrency Interview Questions and Answers (2024)

Concurrency involves executing multiple tasks or operations at the same time or in an overlapping manner.

This blog will teach you the most up to date Concurrency interview questions and will help you nail your next interview.

Q1.

What is concurrency?

Junior

Concurrency is the ability of a system to handle multiple tasks at the same time by managing the execution of these tasks. It enhances resource utilization and requires synchronization mechanisms like locks and semaphores to manage shared resources.
Concurrency is essential in systems like operating systems and databases, where simultaneous task handling is crucial.

Q2.

What is parallelism?

Junior

Parallelism in computing refers to the execution of multiple processes or threads simultaneously, often by using multiple processors or cores. Key aspects include:
- Simultaneous Execution: Tasks run at the same time, not just appearing to do so.
- Hardware Dependent: Typically requires multi-core processors or multiple CPUs.
- Efficiency: Increases computational speed and efficiency for suitable tasks.
- Used in High-Performance Tasks: Ideal for computationally intensive operations or large data processing.

Q3.

What is the difference between process and thread?

Junior

Process: An independent unit of execution with its own memory space.
Thread: A subset of a process that shares memory with other threads within the same process, allowing more efficient execution of parallel tasks.
Key differences:
- Memory Allocation:
  - Process: Has its own independent memory space.
  - Thread: Shares memory space within its parent process.
- Execution:
  - Process: Runs independently and isolated from other processes.
  - Thread: Multiple threads within a process can run concurrently, sharing resources.
- Overhead:
  - Process: More overhead due to memory, resource allocation, and management.
  - Thread: Less overhead compared to processes.
- Communication:
  - Process: Inter-process communication is complex and slower.
  - Thread: Threads can communicate more easily and quickly due to shared memory.

Preparing for a tech interview?👉Top 20 Concurrency questions

Q4.

What is the difference between multi-programming, multi-threading, and multi-processing?

Junior

Multi-programming is about efficiently managing multiple programs in memory.
Multi-threading focuses on executing multiple threads of a single process concurrently.
Multi-processing leverages multiple CPUs to perform different tasks or processes simultaneously.

Q5.

What is thread priority?

Junior

Thread priority is a value assigned to threads that determines their execution order by the operating system's scheduler. Higher priority threads are given preference and executed before lower priority ones.
This mechanism helps in managing the execution of tasks, ensuring critical tasks get more CPU time.
However, it must be used carefully to avoid issues like thread starvation, where lower priority threads get little to no CPU time, and priority inversion, where high priority threads are delayed due to lower priority ones holding necessary resources.

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Q6.

What is context-switching?

Junior

Context-switching is a process where an operating system saves the state of a currently executing process or thread and then loads and executes another. This enables efficient multitasking by allowing the CPU to switch between tasks, especially when one is idle.
However, it introduces some overhead due to the time and resources needed to save and load states. The OS's scheduler manages this process, determining the order of execution for processes or threads.

Q7.

What is Deadlock?

Mid

Deadlock is a situation in computer systems where two or more processes or threads are unable to proceed with their execution because each is waiting for resources held by the others. This results in a standstill, with none of the involved processes able to proceed.
Key characteristics of a deadlock include:
- Mutual Exclusion: Each resource involved is non-shareable and can only be held by one process at a time.
- Hold and Wait: Processes holding resources are waiting to acquire additional resources held by other processes.
- No Preemption: Resources cannot be forcibly taken away from a process; they must be released voluntarily.
- Circular Wait: There exists a circular chain of processes, each waiting for a resource held by the next member in the chain.

Q8.

What is starvation?

Mid

Starvation in computing occurs when a process or thread is perpetually denied necessary resources to progress, often due to scheduling algorithms favoring other processes.
Unlike deadlock, where all involved processes are stuck, in starvation, only specific processes suffer prolonged resource deprivation, leading to indefinite waiting times.

Q9.

What is a thread pool?

Mid

A thread pool is a collection of pre-instantiated, idle threads which stand ready to be given work. These threads are managed by a pool manager. Key aspects of a thread pool include:
- Efficiency: Reduces the overhead of creating and destroying threads for each task.
- Resource Management: Limits the number of threads running concurrently, thus managing resource usage.
- Improved Performance: Can improve application performance in scenarios with a high number of short-lived threads.
- Task Queuing: Tasks are queued and executed as threads become available.
- Control Over Thread Usage: Allows for fine-tuning of the number of threads, balancing system load.

Q10.

What is an atomic operation?

Mid

An atomic operation in computing is an operation that is completed in a single step from the perspective of other threads or processes. Key characteristics include:
- Indivisibility: Cannot be interrupted or observed as a partial operation.
- Consistency: Ensures data integrity by completing fully or not at all.
- Used in Multi-threading: Prevents race conditions in concurrent environments.

Q11.

What is a daemon thread?

Mid

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Q12.

What is a Mutex?

Mid

Q13.

What is a Race Condition?

Senior

Q14.

Describe what is meant by thread-safe.

Senior

Q15.

What is a semaphore?

Senior