Little's law.
also: Littles law · L = λW · L = λ × WItems in a system = arrival rate × time each spends there (L = λ × W): 100 requests/s at 200 ms means 20 in flight.
the two-minute refresher
- L = λ × W: 100 RPS × 0.2 s = 20 concurrent requests.
- 20 workers is exactly at capacity; 150 RPS needs 30, so requests queue.
- Queueing raises W, which raises L: a spiral into failure.
- Size worker pools and connection pools with it.