LLM Bill Increased 10 Question Explained
This worked AI Engineer Interview practice question tests System Reasoning. Try the answer first, then review why B is the best choice.
Short answer
The correct answer is B. Cost per feature per request: tokens in, tokens out, retries, and context size — to find which multiplier moved..
A 10× spend on 1.15× traffic means cost-per-request exploded, and the usual culprits — context growth, retry loops, output length — only show up when you decompose per request by feature. The key is to match the exact action in the prompt to the tool, command, or concept that performs that action directly. Here, B. Cost per feature per request: tokens in, tokens out, retries, and context size — to find which multiplier moved. is the only option that satisfies the scenario without adding unrelated behavior.
The Question
Your LLM bill increased 10× in a week. Traffic grew only 15%. Which decomposition finds the driver fastest?
Why B is correct
A 10× spend on 1.15× traffic means cost-per-request exploded, and the usual culprits — context growth, retry loops, output length — only show up when you decompose per request by feature. The key is to match the exact action in the prompt to the tool, command, or concept that performs that action directly. Here, B. Cost per feature per request: tokens in, tokens out, retries, and context size — to find which multiplier moved. is the only option that satisfies the scenario without adding unrelated behavior.
Why the other options are wrong
Option A does not match the requirement in the prompt. The correct answer is B because A 10× spend on 1.15× traffic means cost-per-request exploded, and the usual culprits — context growth, retry loops, output length — only show up when you decompose per request by feature.
Option C does not match the requirement in the prompt. The correct answer is B because A 10× spend on 1.15× traffic means cost-per-request exploded, and the usual culprits — context growth, retry loops, output length — only show up when you decompose per request by feature.
Option D does not match the requirement in the prompt. The correct answer is B because A 10× spend on 1.15× traffic means cost-per-request exploded, and the usual culprits — context growth, retry loops, output length — only show up when you decompose per request by feature.
Key idea: System Reasoning
Every question is a production situation an AI engineer interviewer can put to you: a failing endpoint, a cost spike, an agent that loops, an eval that disagrees with users. The best answer is almost always the one that measures or contains the problem before it changes the model or the prompt. If you miss a question, note which habit it tests: decompose before you fix, put the security boundary where the side effect happens, and trust an eval only after you check what it covers. The 12 open-ended questions with answer guides are at aijobprep.app/questions/ai-engineer.html.
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