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AI & Machine Learning · Intermediate

Time to First Token (TTFT)

The latency between sending a request and receiving the first generated token.

Definition

TTFT is dominated by the prefill phase that processes the input prompt, so it grows with prompt length. It matters most for interactive applications. Prompt caching and smaller models reduce it.

Exam tip

Long prompts increase TTFT; prompt caching and shorter prompts reduce it.

Related terms