🔥 High-Frequency (Rubrik focus on concurrency & buffer)

1. Implement a bounded/blocking queue using a fixed-size buffer (array + condition variables) jointaro.com+8reddit.com+8reddit.com+8
2. Implement two queues in one fixed-size buffer without wasted space reddit.com
3. Multithreaded Web Crawler with shared visited‑set and task queue
4. Thread Pool implementation with worker threads and task scheduling
5. Readers-Writers lock (fair vs unfair variants)
6. Dining Philosophers / semaphore-based problems
7. Barrier implementation for thread synchronization
8. Promise/Future mechanism in C++/Java (then‑style chaining)
9. Multithreaded LRU Cache (hashmap + doubly-linked list + locking)
10. Multithreaded matrix computation (divide-and-conquer with atomic aggregation)

🚦 Medium Frequency (Still concurrency, but less common)

1. Bathroom problem (gender-based access sync) interviewquery.comreddit.com+2reddit.com+2glassdoor.com+2
2. Semaphore-controlled resource access
3. Producer-Consumer variations (multi-buffer)
4. Concurrent logging system (rotate logs with locks)
5. Thread-safe singleton patterns (double-checked locking)
6. Custom BlockingQueue/BlockingStack
7. Async callback system with threads and queue