答辩：要不要加这层缓存
「这里慢，加个缓存吧」——这个数据能容忍多旧？谁来失效它？
Copy the prompt, then pick a model. It plays the interviewer and asks you through it scene by scene instead of handing you the answer.
On a phone with the app installed, the system opens the app directly. Links cannot open external apps inside WeChat — open it in a browser first.
The copied text ends with the answer key the model grades you against. Don't read it yourself first — working it out on your own is the point.
缓存是拿一致性换延迟，所以提案里得同时回答两边：省了多少（要有基线），代价由谁承担。
它会先把缓存排到别的办法后面：索引看过吗、是不是 N+1、能不能批量、能不能预计算 —— 这四条一条都没试过就加缓存，是在给一个还没诊断清楚的问题贴膏药。
主战场那一问最容易问穿：改这个数据的地方一共有几处？ 后台脚本、别的服务、数据修复的临时 SQL —— 多数人只记得自己那条写路径。
What this one tests
This prompt in the repo (the answer key is at the end of that file — you'll see it)
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Notes from people who did this one
How to use this
The more specific the prompt, the sharper the grading: each specific one carries the root-cause checklist for that kind of situation, and the generic group is the fallback when none of them fits. The system design set grades you on "a benefit with no cost attached means you memorised it"; here the line is different: if you can't give a specific, it's empty.
How to start
- Pick one, open it, copy the prompt.
- Paste it into a brand-new conversation.
- Say in a sentence or two which thing you're going to talk about, then wait for its questions — unlike the system design set, where you say nothing after pasting.
Three commands you can call out at any time
跳过move to the next scene now换一个start over with a different project, outage or experience复盘jump to the wrap-up and print the review card
Three traps
- When it starts consoling you, point it back to the "don't praise me" rule — the two retrospectives are the likeliest to summon a model's soothing persona, which turns the whole thing into emotional support rather than a retrospective.
- Cut it off when it tries to complete your answer for you. You say "I don't remember", it offers "probably because the schedule was tight" — and that sentence is no longer your memory.
- Before pasting a CV or a design doc, strip out phone numbers, email addresses and anything your company wouldn't want leaving the building.
Got a proposal to pitch? Start with defending it. Just finished a project or lived through an outage? Do those retrospectives while you still remember. Job hunting? Audit the CV first, then take the lines that survived into the behavioural drill.
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