I’ve interviewed hundreds of candidates for various software engineering positions, and one of the most annoying situations is when you ask a concrete technical question, and the candidate starts to ramble on unrelated topics instead of just admitting “I don’t know”.

Probably, this is due to a wide-spread advice that you might have heard before: “On a job interview, never admit that you don’t know the answer. Instead, try to guess or keep talking on some related topics”. This is a horrible advice, and here’s why.

If you don’t know the answer and simply start rambling on, this will be immediately obvious for the interviewers. They may get an impression you’re trying to cheat or beguile them. Such behavior might come off as disrespectful.

If you get a direct question, don’t try to avoid the answer or steer the conversation to another topic. Here’s how to properly behave in such situation:

• If you really don’t know the answer, then admit to yourself: you’re no longer in the “knowing” territory, you’re in the “guessing” or “demonstrating proxy knowledge” territory. Don’t try to persuade the interviewer that you “know”, just admit that you don’t.
• If you can come up with a similar topic (“proxy knowledge”), mention this to the interviewer and ask if you should proceed.
• If you feel you could make a good guess (“guessing”), then you could try to, but be honest with the interviewer that this is only guesswork. If they don’t want you to guess, they will say so.

Examples of nice and respectful answers:

• “I don’t really know the answer, but based on common sense / my experience / other tools that I’ve used, I could guess that…”
• “Honestly, I don’t know how it works in this framework / tool / language, but I know how it works in another tool / another framework / another language, should I elaborate?”

To polish the good impression, mention to the interviewer that you’re making a note for yourself to brush up on this question later. Make sure the interviewer sees that you’re interested in learning. This is the best way you can come out of the situation when you just don’t know the answer.

It’s worth mentioning that good interviewers don’t simply base their impression on your answers to direct and concrete questions like “how do you do X using the tool Y?” Such questions are simply too concrete to be useful. But they may lead to great technical conversations, so don’t miss this opportunity. But do it in a respectful and open way.