Mid-level interview question
An upgrade makes your 960-token prefill 5% faster in one before-and-after run. Do you ship it?
Model answer
Not on that evidence. Three runs of the same CPU prefill on our laptop, same model, versions, threads and prompt, gave 219.6, 223.3 and 239.4 ms: 9% apart. Their methods also differed, so no cause could be named. A 5% gap sits inside that spread. Interleave several runs of each version with an identical method, and compare the spreads.
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?
- A vendor says their GPU is twice as fast as your CPU. How would you judge what it buys your workload?
- 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?
- 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.