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Computer science professor who works on fast data processing; co-author of the simdjson parser and a weekly blogger about software performance since 2004.

• simdsearch — A SIMD substring search in a header, and the benchmarks it was built with.

  CommitsCheckout v5; drop paper refs and docs/comment slop · CI on both backends and a bump-driven Release workflow · Package the kernels as a library and fix the review findings

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Systems and developer-tools engineer at Cloudflare as of 2026, on durable infrastructure for AI agents; worked on React and PartyKit before that. Writes at sunilpai.dev.

• It’s been 2 hours and I can already tell this is going to be my most popular post. See the replies. And I’m getting so many DMs from people who went through the same, I’m glad it’s connecting. 2 quick things - - please consider the solution!! it’s counterintuitive and no one considers it but it’s super effective - I hope managers see this too and use it as a tool to help their reports
  Quoting@threepointonenew post: the senior engineer death spiral https://t.co/xzgU1jVBRh a friend just started a big job and asked for some advice. so I braindumped a monologue about a super common failure mode I see with engineers and posted it here, hope it helps whoever it can.

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Computer science professor who works on fast data processing; co-author of the simdjson parser and a weekly blogger about software performance since 2004.

• Faster JSON parsing with SVE2 on ARM processors

  ARM processors, like those in your phone, have instructions capable of processing several elements at once (SIMD). These instructions are called NEON. But many newer processors have a different SIMD extension called SVE…

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Programmer; makes Handmade Hero and teaches Performance-Aware Programming, and argues loudly about how software got slow.

• SIMD Mask Registers

  Although CPUs that support them are still relatively rare by percentage of installed base, mask registers are a powerful feature of modern SIMD hardware well worth understanding.

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Mathematical physicist at UC Riverside. Wrote This Week's Finds in Mathematical Physics and now the Azimuth blog on mathematics, physics and environmental science.

• I'm fascinated by the laurel forests of La Gomera, one the Canary Islands. They're full of different species of trees with shiny, waxy leaves. Mosses and lichens grow on the branches, and the ground is covered with a green mantle of dripping ferns and liverworts thriving in the permanent damp. The place has a mysterious, prehistoric air. The lower altitudes of this island are deserts, but the upper parts catch fog, known locally as "horizontal rain" (lluvia horizontal). Near-constant northeasterly trade winds carry moist Atlantic air that condenses into a persistent low cloud layer. This "sea…

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Writer of Lenny's Newsletter and host of Lenny's Podcast, covering product, growth and career in tech. Previously a product lead at Airbnb. Also an angel investor and advisor.

• My biggest takeaways from Grok @Bot product lead @RomanUgarte_: 1. Two key early product decisions made Grok Bot the success it has become. First, everything runs in the cloud. This means bots can be kicked off from a phone and run while the user sleeps. Second, each bot has access to its own computer. This allows it to operate on tools that have no API because they can simply use the computer the way a human would. 2. “Unshipping” is a big opportunity in product right now. One of the most counterintuitive things the Grok Bot team did in the weeks between internal beta and public launch was r…
  Quoting@lennysanGrok @Bot is the hottest new AI product in the world right now. I'm absolutely hooked. It all started a few months ago as a tiny team holed up in a separate part of the office, building from scratch. Four weeks after the first line of code, the whole company was obsessed. Three weeks later, it laun…

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Programmer; makes Handmade Hero and teaches Performance-Aware Programming, and argues loudly about how software got slow.

• SIMD Masking

  Once we execute both sides of an if/else, we need some way of merging the results.

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Computer science professor who works on fast data processing; co-author of the simdjson parser and a weekly blogger about software performance since 2004.

• simdip — IP parsing benchmarks

  CommitsReject in SIMD instead of re-walking the string · Benchmark ada's current IPv6 parser, not a stale snapshot · Use plain casts in the gather, and store through vpmovwb

  benchmarksRelated

Writes Pedestrian Observations on public transit and why infrastructure costs what it does; a pure mathematician by training, comparing how different countries build.

• Electrification Costs and Confounders

  A presentation by the Bavarian Ministry of Housing, Construction, and Transport (StMB) about expansion plans for the Nuremberg S-Bahn includes several branches to be electrified. Naturally, the presentation includes cos…

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Programmer; makes Handmade Hero and teaches Performance-Aware Programming, and argues loudly about how software got slow.

• Three Steps from Scalar to SIMD

  When we want to change the interior of a loop (with complex control flow) from processing one thing to processing several at a time, it's best to tackle the problem in three sequential steps.

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Software engineer; co-founder and former CTO of Tailscale, previously on the Go team at Google.

• The thing to know about low-level programming is: as you go lower, things actually get *easier*. The difficulty is a mirage. Instead it is maddeningly obscure. You can spend an hour studying to read 6 lines of SIMD and learn all it says is "a + b + c".

  mitchellh.com

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Co-founder of Superlogical, started in 2026 to build server-side terminal infrastructure; creator of Ghostty. Co-founded HashiCorp and created Vagrant and Terraform before that.

• Everyone Should Know SIMD

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Founding member of OpenAI and former director of AI at Tesla; creator of nanoGPT and the term "vibe coding".

• Something I've been thinking about - I am bullish on people (empowered by AI) increasing the visibility, legibility and accountability of their governments. Historically, it is the governments that act to make society legible (e.g. "Seeing like a state" is the common reference), but with AI, society can dramatically improve its ability to do this in reverse. Government accountability has not been constrained by access (the various branches of government publish an enormous amount of data), it has been constrained by intelligence - the ability to process a lot of raw data, combine it with doma…
  Quoting@HrushworthThe British Government is a complicated beast. Dozens of departments, hundreds of public bodies, more corporations than one can count... Such is its complexity that there isn't an org chart for it. Well, there wasn't... Introducing ⚙️Machinery of Government⚙️

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Indian software developer working with React and TypeScript; writes and publishes a newsletter at sreetamdas.com.

• Another fun lil' alias: Quickly switch between git branches, listed in chronological order Suuuuuuper handy and something I use multiple times a day! gist attached:

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Economic historian writing on the Industrial Revolution, the Great Divergence and the origins of modern growth.

• Briefly relaxing my Twitter embargo to suggest that you read @oliverwkim's JMP, on the economic consequences of the Household Responsibility System in China. It's a clever and counterintuitive example of how creative data work can help us answer important historical questions.
  Quoting@oliverwkim🚀JMP alert🚀 My paper w @FergJoel applies machine learning to 1970s-80s satellite imagery to revisit one of the 🇨🇳 Chinese Miracle's first major reforms, the Household Responsibility System—the end of collective socialist agriculture. What we found was quite surprising. 🧵

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