To minimize exposed decode latency when serving $m$ missing experts of size $S$ bytes each, the execution times of the concurrent PCIe cache-fill branch and CPU execution branch are balanced. The cache-fill duration is $T_{\text{fill}}(q) \approx \frac{q S}{B_P}$, and the CPU execution duration on residual bandwidth is $T_{\text{cpu}}(m - q) \approx \frac{(m - q) S}{B_H - B_P}$. Equating the execution times of the two concurrent branches yields:

$\frac{q}{m - q} \approx \frac{B_P}{B_H - B_P}$

Solving for the optimal cache-fill count $q^*$ produces the closed-form policy:

$q^* \approx m \cdot \frac{B_P}{B_H}$

In runtime implementation, $q^*$ is rounded to an integer with a minimum of at least one fill retained to ensure continuous cache warming, dynamically degenerating to pure on-demand GPU caching as $B_H \to B_P$.