Moishe Lettvin

I love coffee, bicycles, cameras and code. I mainly write about technical interviewing here.

The Myth of the Potato

01 February 2021

A few years ago, when I was teaching interview training classes at Etsy, my co-teacher Tim came up with a great metaphor to describe the goal of an interview: by finding the bounds of a candidate’s knowledge, you’re discovering the shape of a “lumpy potato” that describes their knowledge. Every candidate’s potato is unique, and your job as a team of interviewers is to discover the shape of that potato. No individual interviewer can find the whole, but you put your slices together after the panel of interviewers and get the whole potato.

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Remote Interviewing

16 March 2020

First, let me get this out of the way: I’m having trouble writing about anything practical or work-related with everything happening with COVID-19. I’m worried about my family, I’m worried about my friends, I’m worried about neighbors and anyone vulnerable. But this seems like a small, topical thing I can contribute to that might make a narrow sliver of people’s lives a tiny bit easier.

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Unit Tests Aren't Free

19 January 2019

When I was thinking about leaving Google, and interviewing at lots of companies, I tried to ask at least one interviewer per company about unit tests. Google’s culture was very pro-unit test - it was basically impossible to get a PR approved without unit tests, there was a ton of internal documentation and education about how to write unit tests (even in the bathroom. Seriously), etc. etc. - and I thought that I could probably learn some important information about a company’s engineering culture by asking this question. During one of my interviews, the interviewer said, “well, we really don’t have that many unit tests. We have really good monitoring and generally the code coverage of people using our product is better than the code coverage we’d get by adding unit tests, so we’ve built a system where we can see things go wrong very quickly and fix them very quickly.”

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I Don't Know

23 February 2016

As I’ve mentioned before, my co-worker Tim & I teach an interview training class at Etsy. The 2nd most important thing we teach (after “respect the candidate”) is the concept of “mapping the potato” – discovering the boundary between what a candidate knows and doesn’t know, along many many different vectors.

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17 January 2016

Despite being a nerd, I was never all that into reading science fiction and fantasy when I was growing up. Here’s a confession: I’ve never finished a single book by Tolkien or Asimov, though I tried many times in middle school and high school.

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If you see something

02 January 2016

Many years ago, when I was new to interviewing, I did a lunch interview at Google in Kirkland with a guy I’ll call Andrew.

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