Lead developer · SaaS, Next.js & AI
Tsitohaina Kantonirina
I build the systems behind the product.
I take a business need, decide how it should be built, build it, and keep it running in production. Lately that means a whole internal platform for an accounting firm in Paris, started from an empty repo.
What I bring
From spec to production
A short written spec, then a product that is deployed, monitored and used. Not a demo.
The whole system
Interface, API, data and infrastructure in one pair of hands, so nothing falls between two people.
Lead since 2025
Technical direction and a team of five at Genius-At-Work, then a team I hired at the firm. Still hands-on.
Data the business trusts
Pipelines and BI fed from sources the business controls, and AI only where it pays for itself, under a hard cost cap.
§1Selected work
Real projects. Clients are anonymised where they asked, and the screens are illustrations, redrawn for this site.
An internal platform, from an empty repo
One Microsoft sign-in, a shared staff directory and the firm's internal apps, in a monorepo where each app ships on its own.
In use across the firm, and maintained by the team I recruited, onboarded and still lead.
Read the case →Time tracking that payroll relies on
Replaced a SaaS time tracker for the whole firm. Timesheets feed payroll and billing, so the history had to come across intact.
The firm stopped paying per seat and payroll reads from a source it controls.
Read the case →Automation engine for construction companies
A drag-and-drop workflow builder that replaces paper processes in construction companies, with AI extraction of scanned invoices and permits.
Paper approval chains became configurable workflows.
Read the case →An e-learning platform, from code to cloud
Built the platform from the Next.js code to the cloud infrastructure, plus a lead generation engine that fed new enrolments.
Launched and run in production, on infrastructure sized for traffic that arrives in waves.
Read the case →Also built
- 2026Accounting data, near real timeData pipeline, in progress
- 2022Mapping environmental risk zonesGIS, client work
- 2026An assistant for French company dataSide project, AI, in progress
- 2026Waiza, find where to eatSide project, mobile, in progress
- 2026Shipcheck, an audit for AI-built appsConcept, concept
§2What I can do for you
For founders who need a product shipped, and for teams who need it to keep running.
SaaS MVP, from spec to production
A first version real customers can use: sign-in, roles, payments, emails, deployed and monitored.
Fix an app built with AI tools
Your app works in the demo. Before real customers use it, someone should check the code the AI tool wrote.
Internal tools and data automation
Replace the spreadsheets and the SaaS you outgrew with tools your team signs into once, with data your BI can read.
How I work
- Spec first. A short written spec before I code. It saves the meeting nobody wanted.
- Reviewed and tested. I use AI tools every day, and everything I ship is still reviewed and tested against real usage.
- Your data stays yours. No-retention AI providers only, metadata over content when it is enough, and nothing locked in.
- Built to keep running. Monitoring, written decisions, and a team that can maintain it after me. I hire and onboard that team when needed.
§3Experience
Lead developer, Accounting firm, Paris
- Arrived with no code and no team; designed and shipped the firm's internal platform behind a single Microsoft sign-in.
- Time tracking, evaluations, skills and onboarding apps, used by more than 100 people across the firm.
- Recruited and onboarded the team that maintains them.
Lead full-stack developer, Genius-At-Work
- B2B SaaS replacing paper workflows in construction with a drag-and-drop automation engine.
- LLM pipeline extracting structured data from scanned invoices and permits.
- Led a team of five and owned technical direction.
Full-stack and infrastructure developer, Independent, client in Paris
- Built an e-learning platform end to end, from the Next.js code to the GCP infrastructure.
- Built a lead generation engine that fed new enrolments.
Full-stack developer, Independent, client in Paris
- Real-time market dashboard aggregating several exchanges.
- Redesigned the legacy interface traders used every day.
Full-stack developer, NOGAE
- GIS platform for environmental risk zones, used by public agencies.
- Polygon editing, PostGIS validation rules and an approval pipeline.
Full-stack developer, MEDDoC
- Patient and doctor matching with availability, specialty and location filters.
- Cut the booking flow from five screens to two.
§4Stack
- Product and frontend
- TypeScript, React, Next.js, Tailwind CSS, React Native, Vue.js
- Backend and APIs
- Node.js, tRPC, GraphQL, REST / OpenAPI, Laravel, Spring Boot
- Data
- PostgreSQL, PostGIS, Drizzle, Prisma, MongoDB, Power BI
- AI and automation
- Claude Code, Vercel AI SDK, LangChain, Inngest, n8n
- Platform
- Vercel, GCP, Cloudflare R2, Docker, GitHub Actions, Microsoft Entra ID
- Quality
- Vitest, Playwright, Testing Library
§5Education
Master's in Computer Science, Institut Supérieur Polytechnique de Madagascar
Thesis: a web platform for French construction companies
Bachelor's in Computer Science, Institut Supérieur Polytechnique de Madagascar
§6Let's build the next one
Freelance mission, lead role, or an app that needs a second look. Write to me, I answer within a day.
Off screen, I drive. Mostly WRC on a sim wheel, tuning setups the way I tune systems: change one variable, measure, repeat.
This is the plain version of the site, set in Funnel Sans and readable in one pass. Three other versions, a rally stage, an internal platform and an anime sketchbook, load quietly in the background. Their switches appear on the right as each one becomes ready.