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Dan Luu Profile picture
@danluu
Dec 27 • 3 tweets • 2 min read • Read on X
I find it interesting that Matt Walker's Why We Sleep is still widely cited despite Alexey Guzey's fairly convincing rebuttal, "Matthew Walker's "Why We Sleep" Is Riddled with Scientific and Factual Errors"



Even more interesting is Berkeley's responseguzey.com/books/why-we-s…
to Hoiseth, where Berkeley's academic misconduct representative repeatedly makes things up, ending with "I don't wish to go into the weeds...to contest any of your statements", as if whether or not statements of fact are true is just irrelevant weeds.

yngve.hoiseth.net/articles/why-w…

Twitter's alt text limit too short. Please see https://yngve.hoiseth.net/articles/why-we-sleep-institutional-failure/
Twitter's alt text limit too short. Please see https://yngve.hoiseth.net/articles/why-we-sleep-institutional-failure/
And BTW, on Mastodon, where the length limit is longer, I noted that I'm much more pro "getting a lot of sleep" than Guzey and don't find Guzey's arguments for how you can get by on little sleep convincing, but this doesn't make Walker's book or Berkeley's response any good.

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More from @danluu

Dan Luu Profile picture
Dec 5, 2022
I feel like this is true for lots of kinds of conversations and not just tech interviews.

People are correctly pointing out that, if you dig into the logic of basically anything, it falls apart, but that's also generally true of actual humans, even experts.
Sure, is ridiculous, but have you tried asking an expert coach on almost any topic why you should do X?

E.g., try listening to one of the top paddling coaches in the world explain *why* (the what is good, the why is nonsense)
Why do you let the boat "run" between strokes? The explanation is because the boat is moving at top speed when you remove the paddle from the water, so putting the paddle back in slows you down.

But of course this is backwards. The boat decelerates when you're not pulling,
Read 6 tweets
Dan Luu Profile picture
Nov 20, 2022
What are examples of items/categories where you're really getting your money's worth at the high end, not necessarily in terms of utility, but in terms of the difficulty of producing the item more cheaply?

I find the contrast between these vs. "brand" items fascinating.
An example of a category that doesn't qualify but where some items qualify would be high-end fashion, where you're quite often mostly paying for the brand (e.g., an expensive Theory shirt) but there are plenty of items where you're paying for the item (e.g., a $5k Kiton suit).
An example of a category would be high-performance cars (with the notable exception of a few very niche brands like Ferrari, which are famous for having very high margins).

Even if you look at brands that laypeople consider to be "brand" purchases, like BMW,
Read 4 tweets
Dan Luu Profile picture
Nov 16, 2022
Lots of people in my mentions saying things like "Elon is cleaning house! Lazy bums are getting what they deserve!", as if Twitter employees are getting a much deserved comeuppance.

Since people don't seem to understand what the bums at are getting, here's a short primer:
If you look at the people most responsible for Twitter's state, leadership, they had golden parachutes worth tens of millions of dollars

We can debate whether or not they deserve the money, but if you think someone is a lazy bum, cursing them to receive a $10M+ payout seems odd
If we're talking about engineers, Twitter has historically underpaid long-tenured employees relative to BigCo market rate.

The median raise the staff+ people I'm talking to are getting in their new offers is six figures.

Read 5 tweets
Dan Luu Profile picture
Nov 16, 2022
One of the things that I think is sad about the decimation of Twitter eng is that Twitter was doing a lot of interesting (and high ROI) engineering work that, at younger companies, is mostly outsourced to "the cloud" or open source projects

A few examples off the top of my head:
Twitter is, of course, mostly on prem.

The now gutted HWENG group was so good at designing low power servers that, in a meeting with Intel folks, discussing reference designs vs. what Twitter was doing, the Intel folks couldn't believe the power envelope Twitter achieved.
Twitter was operating long before gRPC existed, so they built Finagle. kostyukov.net/posts/finagle-… has some nice explanations and there's been a lot of innovation in Finagle since then.

Twitter still gets a lot of mileage out of owning its RPC layer

Read 19 tweets
Dan Luu Profile picture
Nov 14, 2022
Nice thread about the misconception that major tech companies run systems that can run without intervention because they're automated

The example comes from Google, which is more automated compared than most major companies (MS, etc.), but still quite manual in an absolute sense
One thing that's been interesting about recent events is seeing how people imagine big companies operate, e.g., people saying that Twitter is uniquely bad for not having a good cold boot procedure.

Multiple $1T companies didn't or don't have a real cold boot procedure. @ matthew_d_green Pour one out for Twitter’s cold boot pla[QT previous screenshot] @ahidalgosre Alright. Fine. I’m
One of them is one of the most respected eng orgs on the planet and SREs there wonder if it would take weeks to come back up or months.

As someone who thinks a lot about risks, this isn't how I want the world to be, but it is how the world actually is.
Read 5 tweets
Dan Luu Profile picture
Nov 14, 2022
An interesting thing about this claim is that not only is the implication wrong, Twitter probably has better evidence of its wrongness than any other company in its size class could have.
There are very few companies that have a better distributed tracing setup w.r.t. getting actionable insights on the backend and the ones that have a better setup are much larger (Google, FB, etc.)

Twitter client tracing also punches above its weight.

Of course, the key people who did that work left or got laid off, but it's clear from the data that, if you're looking at why Twitter is so slow in, e.g., India, Uganda, etc., esp. on slow devices, tail latency comes from the network due to unreasonably large payloads + client.
Read 4 tweets

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