I agree with your answer on the rate limiter, but I think it depends on whether the spec is for rolling or fixed one-minute windows. The question is ambiguous,

I agree with your answer on the rate limiter, but I think it depends on whether the spec is for rolling or fixed one-minute windows. The question is ambiguous, but the sample answer implies that we want to track rolling windows. If that's the case, an improvement on the answer is to use a ring buffer instead of a linked list, which allocates a fixed set of memory up front (slower to initialize) but then is allocation-free on each invocation.