Prefill Latency
Definition
Prefill latency measures the time to prepare the input context.
The time for processing the input context until readiness for the first output token.
Simply explained
It describes the waiting time during which the model processes the input before output can begin.
Why it matters in practice
The term contributes to secure, maintainable, and high-performance web applications as well as resilient technical decisions.
Example from business
A service measures prefill separately by input length and hardware.
Limits and pitfalls
- Not defining the measurement point or inadvertently including network and queue time.
Origin & history
Prefill latency became its own operational metric with long contexts and productive LLM inference.
Use in mid-sized companies
- Possible application: A service measures prefill separately by input length and hardware.
Frequently asked questions
What does prefill latency mean?
The time for processing the input context until readiness for the first output token. What mistakes should be avoided? Not defining the measurement point or inadvertently including network and queue time.
Sources
Source checked on 10.10.2026. Editorial application examples are hypothetical; no proof of real customer results.
Editorially reviewed on: