https://ruiyang.co/blog Essays, build logs and field notes on shipping small software, on-device AI, smart contracts, calibration, and the craft of owning a product. en https://ruiyang.co/blog#/sizing-a-bet-you-might-be-wrong-about https://ruiyang.co/blog#/sizing-a-bet-you-might-be-wrong-about essay Sun, 14 Jun 2026 12:00:00 +0000 Knowing your edge is half the job. The other half — how much to actually bet on it — is where most people, and most agents, blow up. https://ruiyang.co/blog#/fsrs-6-and-the-death-of-sm-2 https://ruiyang.co/blog#/fsrs-6-and-the-death-of-sm-2 build log Sat, 13 Jun 2026 12:00:00 +0000 Memdora's scheduler runs on FSRS-6, not the SM-2 algorithm every flashcard app inherited from the 1980s. Here's why I switched and what it changed. https://ruiyang.co/blog#/confidence-is-a-number-you-can-be-wrong-about https://ruiyang.co/blog#/confidence-is-a-number-you-can-be-wrong-about essay Fri, 12 Jun 2026 12:00:00 +0000 Years of actuarial and CFA exams ruined me, productively, for how most software talks about how sure it is. https://ruiyang.co/blog#/a-bug-in-sql-costs-nothing https://ruiyang.co/blog#/a-bug-in-sql-costs-nothing essay Thu, 11 Jun 2026 12:00:00 +0000 Memdora ships on web and iOS. That one fact decided my whole architecture: business logic does not live in the client. https://ruiyang.co/blog#/the-llm-can-write-not-count https://ruiyang.co/blog#/the-llm-can-write-not-count build log Mon, 08 Jun 2026 12:00:00 +0000 For the T3 ADK Dev Challenge I built a multi-agent system whose one hard rule was: the language model never invents a number. https://ruiyang.co/blog#/the-port-that-wouldnt-die https://ruiyang.co/blog#/the-port-that-wouldnt-die code Fri, 05 Jun 2026 12:00:00 +0000 Some bugs you fix in a line. This one took a day, an Objective-C swizzle, and a lecture to myself about whose code actually runs. https://ruiyang.co/blog#/ios-share-extension-silent-save https://ruiyang.co/blog#/ios-share-extension-silent-save build log Mon, 25 May 2026 12:00:00 +0000 Memdora lets you share a sentence from any app and save it as a card. The obvious way to build that was also the wrong way. https://ruiyang.co/blog#/dumb-tasks-deserve-dumb-models https://ruiyang.co/blog#/dumb-tasks-deserve-dumb-models build log Sat, 16 May 2026 12:00:00 +0000 Memdora enriches each card with a model call. For months I reached for the smartest model available. That was the bug. https://ruiyang.co/blog#/memdora-memory-layer https://ruiyang.co/blog#/memdora-memory-layer build log Wed, 15 Apr 2026 12:00:00 +0000 First version stored notes as plain text and searched them with embeddings. It worked. It didn't scale. The second got clever. The third is almost dumb — and correct. https://ruiyang.co/blog#/owning-is-the-hard-part https://ruiyang.co/blog#/owning-is-the-hard-part essay Sun, 15 Mar 2026 12:00:00 +0000 Code is a commodity now. The scarce thing is someone who'll write the spec, name the product, and decide what to cut. https://ruiyang.co/blog#/go-service-pattern https://ruiyang.co/blog#/go-service-pattern code Sun, 15 Feb 2026 12:00:00 +0000 Every Go service I've shipped in the last three years follows the same shape — and I don't think it's just inertia. https://ruiyang.co/blog#/on-device-llms https://ruiyang.co/blog#/on-device-llms field notes Thu, 15 Jan 2026 12:00:00 +0000 A 1.5B-parameter model running on an M2 is now indistinguishable, for the tasks I care about, from a 70B cloud model two years ago. https://ruiyang.co/blog#/chainlink-thin-markets https://ruiyang.co/blog#/chainlink-thin-markets DeFi Mon, 15 Dec 2025 12:00:00 +0000 Chainlink's median-of-medians works beautifully in liquid markets and fails strangely in shallow ones. Here's what I learned shipping Alloyx.