Calculations run on this device. Scenario values are not sent anywhere — the engine is fully local.
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Tail Latency Fan-Out Simulator
Fan a request out to N leaves and watch the tail stretch; then try hedged requests.
Why does one slow leaf decide the request's p99?
Engine 1.0.0 · calculation
10 ms
4 ms
100
30 ms
22ms fan-out p99
- Single leaf p99
- 19.3 ms
- Fan-out p99 (N=100)
- 22.1 ms
- Hedged fan-out p99
- 19.9 ms
- SLO
- Held (30 ms)
“The Tail at Scale”: at 100 leaves, a 1-in-100 slow leaf shows up in nearly every request. Hedging duplicates late requests and takes the first finisher.
Method
- Single-leaf p99 uses the normal approximation mean + 2.326σ.
- Fan-out p99 approximates the expected maximum of N normals with mean + σ√(2 ln N).
- Hedging models E[min of 2] = mean − σ/√π before the same fan-out amplification.