1 piece
When a product is slow under load and adding servers makes the economics worse without fixing the latency, the bottleneck is the work inside one request rather than the capacity to run many. Profile a single request before provisioning anything. On a flight-search product this took the median from 12.8 to 2.8 seconds and database queries per search from 149 to 38, on the same hardware, at roughly a third of the infrastructure cost per search.