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danluu's profile
Dan Luu
Dan Luu
Dan Luu
@danluu

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Dan Luu

@danluu

https://patreon.com/danluu 

danluu.com
Joined December 2008

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    1. Dan Luu‏ @danluu May 26
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      I'm starting to wonder if design interviews are not only useless, but actually contributors to poor design. I'm still thinking through this, by my reasoning for this is:

      5 replies 30 retweets 125 likes
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    2. Dan Luu‏ @danluu May 26
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      There've been times where I've reduced the implementation effort of something by 100x to 1000x, producing in 1 day something that replaced ~1 year of work (proposed or actual). This has never been with "design interview" reasoning, it's always been domain knowledge.

      2 replies 3 retweets 61 likes
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    3. Dan Luu‏ @danluu May 26
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      This doesn't mean you have to be a deep domain expert, in the two most extreme cases, it was something I came to pretty soon after starting work in a new (to me) field. But it was still after much more time than you get in a design interview.

      2 replies 1 retweet 13 likes
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      Dan Luu‏ @danluu May 26
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      Interviewers sometimes try to get around this by saying you should questions assumptions, etc., but I don't think this would have worked in either case. In one case, the solution resolved something that had been an open problem in IR for decades, that's not interview material.

      7:44 PM - 26 May 2020
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      • Sheikh Abdur Raheem Ali James Pitt Matt "MSG superfan" Olson 🌧 Blaize D'souza Keshav Kini LP|Datagram Jacob Matthews
      2 replies 0 retweets 8 likes
        1. New conversation
        2. Dan Luu‏ @danluu May 26
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          In the other case, the solution was to relax an unnecessary constraint. I think it would've been v. difficult to successfully challenge such a fundamental assumption in an interview, it's probably faster to just build the thing (which is what I did), but not feasible in interview

          2 replies 0 retweets 13 likes
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        3. Dan Luu‏ @danluu May 26
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          For my most recent design interview my answers to "how would you scale M up to limit A?" were, in descending order of preference (the interviewers thankfully didn't fail me for this): 1. Buy a solution from N that's known to scale up to 100x A

          1 reply 2 retweets 31 likes
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        4. Dan Luu‏ @danluu May 26
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          2. Talk to expert O, who has solved this problem before, ask for other experts to talk to and see what they have to say 3. Read the relevant bits on LWN and LKML, understand how the open source implementation of M by company P works 4. Run experiments, profile, read code, etc.

          1 reply 0 retweets 28 likes
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        5. Dan Luu‏ @danluu May 26
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          5. The usual design interview nonsense, boxes and arrows, Fermi estimates, say "pubsub" a few times, etc. The interviewers very patiently explained to me that solutions 1-4 were invalid and kindly didn't fail me for those (I think most would've), but what's the point of this?

          3 replies 0 retweets 13 likes
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        6. Dan Luu‏ @danluu May 26
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          I see a lot of systems that look like they were designed by skipping straight to step (5). Of course I can't prove a causal link from design interviews, but it seems plausible that design interviews train people to design real systems without understanding the problem domain.

          3 replies 3 retweets 38 likes
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        7. Dan Luu‏ @danluu May 26
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          People say these interviews "measure how you think", but @hillelogram has looked into the history for other kinds of interview questions, he found "how you think" was a post hoc rationalization for questions that were originally asked for other reasons. Likely same here.

          1 reply 3 retweets 40 likes
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        8. Dan Luu‏ @danluu May 26
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          But even without looking at the historical record, "how you think" seems bogus To answer a Fermi estimation question, you just need to know how to play the Fermi estimation game. Make up numbers, multiply them together, and then you pass. Basically ditto for design interviews.pic.twitter.com/zoOU85g5ac

          On the hiring side, we found that brainteasers are a complete waste of time. How many golf balls can you fit into an airplane? How many gas stations in Manhattan? A complete waste of time. They don’t predict anything. They serve primarily to make the interviewer feel smart.
…
Fun fact: in business school, I got asked that exact brain teaser by some company (I can't remember who). "Can I take a minute?" I asked.
"Sure," said the interviewer. After a moment, I said, "nineteen". He looked confused.
"How did you get that answer?" he asked. I looked confused.
"I counted."
Presumably he hadn't been expecting to interview someone who grew up in Manhattan, went to school in the Bronx, and spent a lot of time driving around New York with her dad.
I didn't get the job. Apparently, they were looking for people who used some process other than arithmetic to figure out how many gas stations there were in Manhattan.
          6 replies 14 retweets 85 likes
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        9. End of conversation
        1. New conversation
        2. rntz‏ @arntzenius May 27
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          Replying to @danluu

          IR=?

          1 reply 0 retweets 0 likes
        3. Dan Luu‏ @danluu 20h20 hours ago
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          Replying to @arntzenius

          https://en.wikipedia.org/wiki/Information_retrieval …

          0 replies 0 retweets 1 like
        4. End of conversation

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