A junior asks why the partition key matters.
You know the answer. You also have four other things open, so you paste them a clear explanation from a chat window and go back to what you were doing.
The explanation is good. It is probably better written than what you would have said out loud. The junior reads it, says thanks, and moves on.
Something did not happen, though, and it will be about a year before anyone notices.
🔍 What the forward leaves out
Here is roughly what you would have said if you had spent the five minutes.
You would have started with the query patterns, because the partition key is not a property of the table, it is a bet about how the table gets read. Then you would have mentioned the time we partitioned by customer ID and produced two million tiny files, and what that did to the metadata layer, and how long it took to find. Then you would probably have asked them what they thought the query pattern was going to be in a year, and let them be wrong about it, and then talked about why.
The pasted explanation contains the first part. It cannot contain the second, because it does not know about the incident. And it cannot contain the third at all, because the third is not information. It is the junior thinking, badly, in front of someone who can see where the thinking goes wrong.
That third part is the whole thing. The answer to the question was never the point.
🧠 Why this lands on seniors
Two reasons, and the second is the uncomfortable one.
You are the only person who can make this trade. Nobody else on the team is being asked the question. The junior cannot choose to be mentored by someone who is not there.
And you are the only person who pays for it, twelve months out. This is what makes it different from most decisions about your own time. Skipping a code review costs you today. Skipping this costs you next year, when you need someone to own a system and find that nobody on the team can reason about it without help.
There is evidence this is happening broadly and not just to you. A study by researchers at UC Berkeley and Yale, published in Harvard Business Review in early 2026, tracked 200 employees at a technology company over eight months. One of its findings was direct: rather than mentoring juniors, senior engineers were spending hours reviewing and fixing AI-generated code. The mentoring time did not disappear into leisure. It went into review.
A paper in Communications of the ACM the same month described the mechanism from the junior's side. They meet a problem beyond their current ability. A working solution arrives in seconds. They ship it, the review passes, the ticket closes, and the mental model that the difficulty was going to build never gets built. Everything about that sequence looks like success.
✅ Prepare with it, do not send it
The rule is small, because a rule that costs 20% of your week will not survive contact with your actual week. Research on mentoring load puts a junior at roughly 20 to 30% of a senior's time in the early months, and I am not going to pretend this fits in that budget. It is smaller than that on purpose.
When a question comes in that has a reasoning answer rather than a factual one, do not forward. Take five minutes.
Use the chat window to prepare, not to reply. Ask it to lay out the tradeoffs so you have them straight, especially if the area is one you know by instinct rather than by explanation. That is a genuinely good use, and it takes thirty seconds.
Then run the five minutes like this:
Ask before you answer. "What do you think happens if we partition by customer ID?" Let them answer. If they are wrong, that is the useful part, and you have now found the actual gap rather than the one they asked about.
Give one thing that is not in any documentation. The incident. The migration that went badly. The reason your team does it differently from the way the internet does it. This is the part no tool has, because it is not written down anywhere.
Stop. Five minutes. You are not running a class.
The test for whether a question needs this: could a correct answer still leave them unable to make the same decision themselves next time? If yes, it is a conversation. If it is "what is the syntax for a window frame," forward it and think nothing of it.
⚖️ The objection worth taking seriously
The weak version is "I am their lead, not their tutor, and they can read." Answerable in one line, so it is not the real argument.
Here is the real one. On-demand explanation is unlimited, instant, patient, and free of social cost. Senior mentoring is scarce, inconsistent, badly delivered about half the time, and requires a junior to admit ignorance to the person who writes their review. For a junior who is remote, or in a different timezone, or simply not confident, the chat window may be far better access to explanation than they would ever have got from you.
I think that is largely correct, and it is worth conceding fully rather than partly. Measured as access to explanation, this is a clear improvement over what most juniors had before, and the people it helps most are the ones who were least likely to ask.
The concession has a limit, though, and the limit is what explanation is. Explaining is answering the question that was asked. What the five minutes does is different: it finds the question they did not know to ask, supplies the history that is not written down anywhere, and lets them be wrong in front of someone who can see why. Judgment gets built by watching decisions get made and seeing the results turn up later. That is not a thing that can be retrieved, because it is not information.
So the honest position is not that the chat window is worse. It is that it is better at one of these two things and cannot do the other at all, and the one it cannot do is the one that turns a junior into someone you can hand a system to.
There is also a signal worth watching. A 2026 survey found 56% of HR leaders reporting that early-career hires turn to unofficial AI tools when guidance is unclear. If the guidance is not there, the chat window fills the space, and it fills it with answers rather than judgment.
🎯 The takeaway
Prepare with it. Do not send it.
1. Sort the reasoning questions from the factual ones. Test: could a correct answer still leave them unable to decide this themselves next time?
2. For reasoning questions, take five minutes. Use the chat window to get your own thinking straight first. That part is fine and fast.
3. Ask before you answer. Their wrong answer tells you where the actual gap is.
4. Give one thing that is not written down anywhere. The incident. The reason your team does it differently.
The pasted explanation answers the question. The five minutes is what makes the question stop being asked.
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