A staff engineer I respect was asked, in a room full of people, how long a migration would take. He said, “I don’t know yet. I’ll have a real number Thursday after I’ve looked at the foreign keys.” Nobody blinked. The meeting moved on. A junior engineer watching that exchange later told me it rewired something for him, because he’d spent two years believing that sentence was the one thing you could never say.
I believed it too, once. Early career, “I don’t know” felt like the admission that gets you found out, the crack that reveals you don’t belong. So I did what scared engineers do: I guessed with confidence. I gave the number that sounded competent instead of the number that was true, and I committed to designs I didn’t understand because asking felt more dangerous than being wrong later. Later always came.
The two-word difference#
The fear isn’t entirely wrong. There’s a version of “I don’t know” that does read as junior, and it’s the one that stops there. “I don’t know” as a full sentence, with a shrug, hands the problem back to the room and waits for rescue. That one earns the reaction the junior is afraid of.
The senior version has two more words and a different posture: “I don’t know yet.” It’s not an exit. It’s a status. It says the answer is knowable, I know how to get it, and here’s when you’ll have it. That sentence projects more competence than a confident guess, because everyone experienced in the room knows the confident guess is fiction and they’re quietly downgrading the person who offered it.
The full senior script is three parts. Admit the gap, name the path, commit to a time. “I don’t know how long the data backfill takes. It depends on row count and whether we can batch it, so let me run a count and prototype the batch tonight, and I’ll have an estimate by tomorrow standup.” That is not a person who’s lost. That’s a person who’s already working.
Why it’s load-bearing for a team#
The cost of the confident guess isn’t just that it’s wrong. It’s that it teaches everyone watching that this is a place where you perform certainty instead of pursuing it. Juniors calibrate hard on what seniors do. If the senior engineers guess with conviction and never say “I don’t know yet,” the juniors learn that the way to be senior is to never admit a gap, and now you have a whole team optimizing for sounding sure over being right. That’s how you get an estimate culture nobody believes and a design review where the real concerns go unspoken.
When a senior person says “I don’t know yet” cleanly and then comes back Thursday with the number, they’re not just answering the question. They’re licensing everyone junior to do the same, which is the only way you find out what your team actually doesn’t know before it ships.
Where it’s genuinely hard#
I won’t pretend the calculus is always clean. There are rooms where uncertainty gets punished regardless of how well you frame it, where an executive wants a number and “yet” reads as evasion. The move there isn’t to abandon the truth, it’s to bound it: “worst case three weeks, best case one, and I’ll tighten that by Thursday.” You’re still refusing to fabricate precision you don’t have. You’re just meeting the room’s need for a range it can plan against.
And there’s a real failure mode on the other side, the engineer who hides behind “I don’t know yet” to avoid ever committing to anything. The tell is the missing third part. If “yet” never resolves into an actual answer by the time you promised, it wasn’t intellectual honesty, it was procrastination with better branding. The move only works if Thursday’s number actually arrives.
What I tell the junior version of me#
The thing I wish someone had told me at twenty-four: the people whose competence you’re afraid of are the ones saying “I don’t know yet” the most. They’ve said it enough times, and delivered the answer enough times, that it stopped costing them anything. The confidence you’re trying to fake is the thing that grows on the far side of admitting the gap honestly, over and over, until it’s just how you talk.
You don’t earn the right to say “I don’t know yet” by becoming senior. Saying it well, and then doing the work, is a large part of how you get there.
