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Three clients
Machi's Web, iOS and Android clients share one API and content model.
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Independent developer / life in Japan
I turn small, stubborn ideas into shipped products.
I live in Japan, write code, and build products of my own. Machi is a local community for city life; Shangence helps people think through business risk before opening a shop or starting a venture. This site is not a static resume. It is where I keep the work, the technical notes, the trade-offs, and a few observations from life here.
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live products
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public repos
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Machi clients
Verifiable signals
The first version, the launch, the fixes, the quiet maintenance after launch — those details leave a trace.
Machi's Web, iOS and Android clients share one API and content model.
Shangence includes assessment, Stripe JPY payments, PDF reports and admin review.
AWS, Nginx, systemd, certificates, backups and deploy scripts are maintained by me.
This site includes trilingual content, search, SEO, admin tooling and a copy editor.
Work
Machi and Shangence are the two products I build solo. yaokai.me is this personal site and CMS. The work page separates Machi into Web, iOS, and Android, and explains the choices behind each part.
Housing, second-hand, jobs, local services and community in one city space. Three clients — Web, iOS, Android — share 80+ REST + SSE endpoints, with media on S3 + CloudFront.
Solo: product design, all three clients, backend, database, AWS.
Next.js 15 · SwiftUI · Kotlin / Compose · Python · SQLite → PostgreSQL · AWS
Helps people starting a business in Japan see their risk clearly: a 7-step assessment, rule-engine scoring, paid reports (Stripe JPY + PDF), admin review and refunds. Legal pages and PII masking included.
The full commercial loop, from business design to legal compliance.
Next.js App Router · React Hook Form / Zod · Prisma 7 / PostgreSQL · Stripe JPY · Vitest
The site you are reading. Next.js 16 + Prisma, three languages, its own writing admin, deployed on Lightsail in Tokyo.
The resume's design system, ported to the web. Open source.
Next.js 16 · Prisma · Tailwind CSS · i18n (zh / ja / en) · Lightsail
Scope
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Talk to real users, turn vague ideas into specs you can build from.
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Next.js for web, SwiftUI for iOS, Kotlin for Android — one shared API.
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Python APIs, PostgreSQL / SQLite, auth, notifications, media uploads.
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AWS, Nginx, systemd, domains and certificates. I debug my own outages.
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Stripe payments, admin consoles, audit logs, legal pages.
Writing
Bugs I ran into, product trade-offs, notes from job hunting in Japan, and small observations from the places I live through.
Contact
Email is fastest. Reading through the work first is perfectly fine too.hi@yaokai.me