Concurrency & Multithreading Interview Sheet

Threading and concurrent-systems practice for interviews, organized by theme, with progress tracking saved on this device.

Concurrency questions test whether you can reason about correctness when execution order isn't guaranteed — race conditions, deadlocks, and the synchronization primitives that prevent them. A few of these map to real coding problems; most are design exercises worth talking through out loud.

0 / 50 completed

Threading (6)

Print in Order easy
Print FooBar Alternately medium
Print Zero Even Odd medium
Building H2O medium
Fizz Buzz Multithreaded medium
Traffic Light Controlled Intersection medium

Synchronization (6)

Design Bounded Blocking Queue medium
Design Readers-Writers Lock hard
Design Semaphore medium
Design Mutex medium
Design Atomic Counter medium
Design Barrier hard

Parallel Programming (6)

Parallel Matrix Multiplication hard
Parallel Quicksort hard
Parallel Merge Sort hard
Parallel DFS hard
Parallel BFS hard
Parallel Dijkstra hard

Concurrent Data Structures (6)

Design Concurrent HashMap hard
Design Concurrent Queue medium
Design Concurrent Stack medium
Design Concurrent Trie hard
Design Concurrent BST hard
Design Concurrent LRU Cache hard

Async Programming (6)

Design Async Queue medium
Design Async Cache medium
Design Async Database hard
Design Async File System hard
Design Async HTTP Client medium
Design Async Task Scheduler hard

Deadlock Prevention (6)

Dining Philosophers Problem hard
Banker's Algorithm hard
Resource Allocation Graph hard
Deadlock Detection Algorithm hard
Deadlock Recovery hard
Lock Ordering Strategy medium

Performance Optimization (6)

Lock-Free Data Structures hard
Memory Barriers hard
Thread Pool Optimization hard
Cache Coherence hard
False Sharing Prevention hard
Work Stealing Algorithm hard

Real-World Concurrency Patterns (8)

Design a Thread-Safe Token Bucket Rate Limiter medium
Design a Distributed Lock (Redis/Zookeeper Style) hard
Design a Leader Election Algorithm hard
Implement a Read-Write Lock from Scratch medium
Design a Lock-Free Counter Using Compare-And-Swap medium
Design a Thread-Safe Connection Pool medium
Design a Single-Threaded Event Loop (Node.js Style) hard
Design a Simple Actor Model System hard