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Scalability (Amdahl and USL)
Predict how throughput grows as you add nodes or threads, and where adding more starts to hurt.
Performance & capacityHow it's worked out
- C(N) = N ÷ (1 + σ(N − 1) + κN(N − 1)). Peak N* = √((1 − σ) ÷ κ). Amdahl limit = 1 ÷ σ
- Coefficients fitted from measured throughput
NoteFit sigma and kappa from a few load-test points, then use the model to plan. Past the peak, adding nodes reduces throughput.
Source: Gunther, Universal Scalability Law; Amdahl (1967)
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