Prefill-as-a-Service: How KVCache Goes Cross-Datacenter
Deriving PrfaaS-PD from the ground up — why the KVCache transfer bandwidth wall confines PD disaggregation to a single RDMA island, how hybrid attention lowers the KV throughput enough to cross that wall, the selective offloading principle, the three-stage producer-consumer throughput model, the optimality conditions for routing threshold and prefill/decode ratio, and the dual-timescale scheduler — all derived step by step with one tiny two-cluster deployment.