Senior interview question
A provider's status page shows a p50 TTFT of 180 ms. You need 300 ms for 9 in 10 of your users. What do you do before signing up?
Model answer
Measure it myself: their number is their workload on their day. Latency depends on my prompts and sampling settings, so I'd send my own prompts at my lengths and concurrency and measure p90 TTFT, as the book's criteria table does on an internal prompt dataset.
Test at peak concurrency, since some providers throttle. Check quality too: the same Llama models scored differently across providers in a Cerebras experiment. Compare cost per request, not per token.
Practise the rest
11 Benchmarking questions, 492 in all, each with a model answer. Free.
More Benchmarking interview questions
- What does a fair inference benchmark hold fixed?
- An upgrade makes your 960-token prefill 5% faster in one before-and-after run. Do you ship it?
- A vendor says their GPU is twice as fast as your CPU. How would you judge what it buys your workload?
- In the capstone, continuous batching with at most 8 seats gives a p90 first token of 122 ms against a 300 ms target, yet the planner marks it failing. Why, how do you fix it, and what would you measure first on the real system?
- What does perplexity measure, how do tokenizers distort it, and where does it break down as a quality metric?
- Design optimised inference pipelines, and tell me how you would benchmark them.