As call volumes increase, the agent should scale without crashing or significantly slowing down. Test the system’s performance at high concurrency – e.g., simulate peak hour traffic with many parallel calls. Monitor CPU/memory usage, queue lengths, and any infrastructure failures (like speech recognition service not responding or the system resetting). KPIs here might include max concurrent calls supported at a given latency, or throughput (calls/hour) until degradation. Also, test long call durations to ensure no memory leaks or quality degradation over time (does a conversation lasting 30 minutes perform as well as one of 2 minutes?). Any failure (like the agent dropping the call or restarting mid-conversation) should be recorded. Essentially, this is reliability testing – the agent should be as reliable as a phone switch in a call center. Uptime and error-free transaction rates can be metrics to report.