| 1 | How does the event loop decide what to run next? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Intermediate |
| 2 | What's the relationship between requestAnimationFrame and the event loop's rendering step? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Advanced |
| 3 | Why does a long synchronous function block UI updates and event handling? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Intermediate |
| 4 | Is JavaScript single-threaded, and what does that mean in practice? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Beginner |
| 5 | What is the call stack? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Beginner |
| 6 | What is the difference between the microtask queue and the macrotask (task) queue? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Intermediate |
| 7 | Why does Promise.resolve().then(cb) run before setTimeout(cb, 0), even with a 0ms delay? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Advanced |
| 8 | How would you break a large synchronous task into chunks to keep the UI responsive? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Advanced |
| 9 | What is 'starvation' of the macrotask queue, and how can recursive microtasks cause it? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Advanced |
| 10 | How does async/await map onto the microtask queue under the hood? JavaScript › Event Loop & Concurrency | JavaScript | Event Loop & Concurrency | Advanced |
| 11 | What is the difference between concurrency and parallelism, and which one does Node.js's event loop actually provide by default? Node.js › Event Loop & Non-blocking IO | Node.js | Event Loop & Non-blocking IO | Beginner |
| 12 | What is the difference between how Node.js handles I/O-bound concurrency versus CPU-bound work, and why does this distinction shape Node.js's ideal use cases? Node.js › Event Loop & Non-blocking IO | Node.js | Event Loop & Non-blocking IO | Advanced |
| 13 | How does asyncio's event loop schedule and switch between multiple coroutines, and what makes this cooperative rather than preemptive? Python › Concurrency (asyncio/threading/multiprocessing) | Python | Concurrency (asyncio/threading/multiprocessing) | Advanced |
| 14 | How do you safely run a blocking, synchronous function from within an asyncio coroutine without freezing the event loop? Python › Concurrency (asyncio/threading/multiprocessing) | Python | Concurrency (asyncio/threading/multiprocessing) | Advanced |
| 15 | How would you use concurrent.futures.ProcessPoolExecutor together with asyncio to run CPU-bound work without blocking the event loop? Python › Concurrency (asyncio/threading/multiprocessing) | Python | Concurrency (asyncio/threading/multiprocessing) | Advanced |
| 16 | How does Node.js achieve high concurrency for I/O-bound workloads despite running JavaScript on a single main thread? Node.js › Node.js Fundamentals & Runtime Architecture | Node.js | Node.js Fundamentals & Runtime Architecture | Advanced |
| 17 | How do you run multiple async iterators concurrently and merge their results? JavaScript › Async Iterators & Streams | JavaScript | Async Iterators & Streams | Advanced |
| 18 | Why can errors thrown inside a setTimeout callback NOT be caught by a surrounding try/catch? JavaScript › Error Handling | JavaScript | Error Handling | Advanced |
| 19 | Why can setInterval() be a subtle source of memory leaks, and how do you avoid it? JavaScript › Memory Management & Garbage Collection | JavaScript | Memory Management & Garbage Collection | Advanced |
| 20 | How does a WebSocket connection differ fundamentally from repeated fetch() requests? JavaScript › Networking: Fetch, XHR, WebSockets & CORS | JavaScript | Networking: Fetch, XHR, WebSockets & CORS | Advanced |