Where is Feed-Forward Network used in practice?

The MoE family replaces the dense FFN with a routing layer that selects a small subset of "expert" sub-FFNs per token, dramatically reducing active parameters during inference while maintaining total capacity. AI governance teams encounter FFN architecture choices in model lineage documentation; the specific FFN variant (dense vs MoE, ReLU vs GELU vs SwiGLU) significantly affects compute, memory, and behavior. T