Junior interview questionAsked by candidates · collected on GitHub
A chat reply streams in token by token. What two waits does the user feel, and which one does streaming make matter most?
Model answer
Time to first token (TTFT), mostly prefill, and total latency, mostly decode. Streaming makes TTFT the visible wait: on our test laptop's CPU, GPT-2 small's first token arrived at 67.5 ms, the last at 633 ms. A fast reader takes about 120 ms per token, so tokens needn't arrive much faster than that.
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