Kacam.net

System design

订单与库存(电商交易链路)

一条链路跨四个服务,中间任何一步都可能失败。

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.

考的不是「知不知道 Saga」,是补偿本身失败了怎么办 —— 这一层答不上来,前面说的都是名词。

建议排在支付之后:那道题里的幂等和对账,这道会接着用。

★★★★☆ · about 50 min · Tests: 跨服务长事务、Saga / TCC、快照、状态机、分摊取整

Cross-cutting patterns this one leans on

Consistency and compensation State machines and timeout compensation Idempotency Sharding and distributed IDs Money and numbers Message queues

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Notes from people who did this one

Nobody has written yet. After you run it, say what came out of the conversation — which scene stumped you, which conclusion you changed afterwards.

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How to use this

How to start

  1. Pick a question, open it, copy the prompt.
  2. Paste it into a brand-new conversation — not one where you already discussed this question, or the model follows your old answers.
  3. Say nothing. Wait for its first question.

Four commands you can call out at any time

  • 跳过 move to the next scene now
  • 提示 give a direction, not the answer
  • 直说吧 spell this point out in full, then keep pressing on the trade-offs
  • 复盘 jump to the wrap-up and print the review card

Three traps

  • Don't do two questions in one conversation — context from the first makes the model prejudge your level.
  • Don't look up the answer the moment it asks. Being stuck for 30 seconds is itself useful information.
  • When it starts praising you, point it back to rule five — feeling validated crowds out noticing what you missed.

Suggested order: start with the cross-cutting drill as a parts test, use the short-link question to get used to the flow, then pick by the direction you interview for, and keep redoing the one about your own project.