Performance

Load testing showed latency growing linearly with concurrency: the server was serializing, capping throughput at about 8 requests per second.
Three structural fixes: parallelize independent ONNX inference calls, replace a reference-counted five-thread dispatcher with single-threaded cooperative multitasking, and run several independent backend instances.
Latency curve went from linear to roughly square-root in concurrency; sustained throughput reached 64 to 80 requests per second on the same hardware, an 8 to 10x improvement.
Single-request latency barely moved (about 90 to 70 ms). This was a contention fix, not a per-request speedup.