A voice agent that felt broken on every first turn, and the latency budget I had to take apart stage by stage to find the two dead seconds.
The bug report was one sentence: "callers keep talking over the greeting." I listened to the recordings and heard the same shape every time. The phone connects. The caller waits. One second of nothing. Two seconds of nothing. Then, right as the caller gives up and says "hello? are you there?", the agent starts its greeting, and now both of them are talking, and the whole call opens in a collision.
Nobody was talking over the agent to be rude. They were talking over it because they thought the line had dropped. Two seconds of dead air on a phone call is an eternity. People fill it.
I had a name for the number that was killing me before I knew its value: time to first audio byte. The gap between the caller finishing their turn and the first sample of the agent's voice actually reaching their ear. On this system it was around 2 seconds on the opening turn, and it felt every bit that long.
Timing the pipeline instead of guessing
