Calculations run on this device. Scenario values are not sent anywhere — the engine is fully local.
inference calculator · free
Back-of-the-Envelope Estimator
Turn QPS, fan-out, and per-request cost into a defensible capacity number.
How many servers does this traffic estimate really need?
Engine 1.0.0 · calculation
2,000 QPS
3 leaf calls
One incoming request multiplies into this many leaf requests.
4 ms
50 %
Utilization ceiling you refuse to plan past.
3machines (16c) at 50% headroom
- Leaf traffic
- 6,000 QPS
- Cores busy at peak
- 24
- Cores to provision
- 48
- Rule used
- Little's LawL = λW
Concurrency = rate × latency. Provision for the leaf tier, not the edge: fan-out is the multiplier people forget.
Method
- Little's Law: concurrent leaf work = leaf QPS × per-call core seconds.
- Provisioned cores divide busy cores by target headroom; machines assume 16 cores each.
- Fan-out is applied before capacity math — the edge QPS is never the provisioning input.