Question Bank

Every question, one list

Sandboxed coding rounds that run against a hidden test suite, and written questions graded against a rubric — side by side, because when you are drilling a topic you want both.

9 questions · browse by bank instead

• Bounded producer-consumer queueCondition variables, and the two mistakes almost everyone makes: waiting without a predicate, and signalling with the lock held.mediumWrittenExplain to unlock#c++#concurrency#condition-variable25 min
• Design a rate limiterSmall surface, deep follow-ups. The distributed counter race is the real question.mediumWrittenExplain to unlock#concurrency#hld#reliability45 min
• Design an LRU cacheO(1) get and put. Then the follow-up nobody prepares for: make it thread-safe.mediumWrittenExplain to unlock#caching#concurrency#data-structures30 min
• When is an atomic not enough?Everyone can say "an atomic is lock-free and cheaper". The question is what a mutex gives you that a pile of atomics does not.mediumWrittenExplain to unlock#atomics#c++#concurrency15 min
• Why did my counter get slower with more threads?Eight threads, eight separate counters, no locks — and throughput falls off a cliff. This is the question that finds out whether you know what a cache line is.mediumWrittenExplain to unlock#c++#cache#concurrency20 min
• Design a ticket booking systemInventory correctness under a thundering herd. Overselling is the failure to design against.hardWrittenExplain to unlock#concurrency#consistency#hld45 min
• The ABA problemYour compare-and-swap succeeded. That does not mean nothing happened.hardWrittenExplain to unlock#atomics#c++#concurrency25 min
• Was double-checked locking ever actually broken?A famous bug, a famous fix, and a much simpler answer almost nobody gives.hardWrittenExplain to unlock#c++#concurrency#memory-model20 min
• What does memory_order_relaxed actually guarantee?The question that separates people who have used atomics from people who understand them.hardWrittenExplain to unlock#atomics#c++#concurrency25 min