Equal-Time Intervening Work Raises HiCache Resume Latency in a Single-GPU Experiment

Research object

Methods: randomized paired idle-versus-intervening-cold-prefill comparison; each arm used a distinct target prefix, six pressure requests, and a fixed two-second pause before continuation. The independent unit was the paired session block (n=20); the primary statistic was the median paired TTFT difference with a percentile bootstrap over blocks. Results: treatment-minus-idle median +1,318.912 ms (95% CI +604.540 to +1,458.767 ms), with 20/20 positive pairs; load-back evidence recorded for 40/40 continuations. Conclusion: in this constructed single-A100/SGLang/Qwen3-8B workload, unrelated cold work during the pause raised cached-continuation TTFT. The experiment does not isolate the internal latency pathway and does not establish predictive-scheduler benefit, production SLO impact, or generality. The manuscript documents the missing full server-log limitation.