Time to First Token

Why production chat UIs stream tokens token by token instead of returning the full reply

P99 TTFT spikes every Tuesday at 9am, order the triage steps

Name the dominant cost driver of GPT-5.5 latency at a 200k-token input

What does the first forward pass set up that the second one doesn't pay for?

TTFT: name the metric it captures and what dominates it

Server-Sent Events streaming: define it and explain why chat APIs default to it

End-to-end latency: fill in the queue, prefill and decode components.

Does Anthropic's message_start event count toward TTFT in production benchmarks?

Match TTFT and TPOT to the latency they measure during streaming

Define TTFT, TPOT and throughput. Which should a chatbot vs a batch summarizer optimize?

A chatbot team reports TTFT P99 jumped from 300ms to 1.4s overnight. Which root cause is most likely?

Which prompt-construction pattern is most likely to actually hit the provider's prompt cache?

What traces and metrics do you need to debug a P99 TTFT regression in production LLM serving?

Which metrics are essential to debug a P99 TTFT regression in production LLM serving?

For a 200-token prompt and 1000-token completion, why does decode dominate end-to-end latency?