Time to first byte

What time to first byte means

Time to first byte is the serving concept concerned with time to first byte during AI inference. In a serving system, define the measurement boundary before collecting data. State whether the worker is warm, which model and precision are active, how batching is configured, and whether the request is streamed. These details determine whether two similar measurements describe the same operating condition.

How it appears in a workload

A team can compare a quiet run with a burst of representative requests and observe how time to first byte changes. Record relevant timestamps and runtime signals with the request rather than relying on one dashboard aggregate. A useful comparison includes request mix, arrival pattern, concurrency, and output limits. For routed traffic, retain the selected route so a change can be investigated rather than attributed to time to first byte without evidence.

Limitations and tradeoffs

It should be interpreted with error rate and user-visible latency because an isolated gain can move cost or tail behavior elsewhere. Use it with p50 and tail latency, useful token throughput, errors, memory pressure, and cost. The best configuration is the one that meets the application's reliability and responsiveness requirements under representative traffic.