CS fundamentals and algorithms
Streaming moving average
Frame times arrive as a stream, one per frame. Design a type that returns "the average of the last k frames" instantly whenever asked. It's called 60 times a second, so the math has to stay light. Explain the data structure, how you update it, and the complexity.
How would an interviewer hear this answer? You'll see whether they'd move on, dig in, or say no, and which sentences would trip you up. Your score doesn't change.