Did back of envelope capacity math for a real incident at work and it clicked way harder than any system design mock ever did

Spent months doing system design mocks where the throughput numbers always felt made up, just plugging in round numbers because that's what the guide said to do. Then an actual on-call incident needed me to estimate whether a queue could handle a traffic spike before it fell over, real numbers, real consequences. Same math, completely different feeling. Wish someone had told me to care about the arithmetic before it actually mattered.