Teodor Halvik
Full-stack engineer · Rotterdam
I help product teams ship interfaces that load fast and stay maintainable. Independent since 2024, previously at Merrowgate and Kova Supply.
Shipping production code
Products shipped
GitHub stars on open source
// selected work
Six projects from 2023 to 2025: client work, open source and a few things built for fun.
Web app
·
2025
Kova Checkout
A rebuilt checkout for a B2B supplies shop that loads in about a second and stopped paging the engineers on call.
Next.js · Stripe · Playwright
Open source
·
2025
Hookline
An open source webhook inspector: point any service at a Hookline URL, watch requests arrive, replay them and diff payloads.
Go · SvelteKit · SQLite
Design system
·
2024
Mareld UI
A component library for a health technology company’s patient and clinician apps, built on Radix and documented in Storybook.
React · Radix · Storybook
Backend
·
2023
Merrowgate API v2
The second version of a payments API, designed from the contract up so the docs, SDKs and server can never drift apart.
Node.js · PostgreSQL · OpenAPI
Open source PWA
·
2025
Ferrynote
A small notes app that works fully offline, syncs when it can and fits in an 18 KB core.
TypeScript · React · IndexedDB
Side project
·
2024
Transit Pulse
A live map of Rotterdam’s trams and buses built from the open transit feed, smooth even on a budget phone.
TypeScript · MapLibre · Deno
// about
Good software feels boring to its users. I do the interesting part so they don’t have to.
I have spent nine years shipping production code for payments, health and logistics teams across Europe. I like small teams, clear problems and codebases the next person can understand. Most days that means TypeScript in the browser, Go or Node on the server and Postgres underneath.
languages
TypeScript
Go
SQL
frontend
React
Next.js
Svelte
Tailwind
infra
Postgres
Vercel
AWS
Docker
// services
Product engineering
Full features end to end, from schema to UI.
Front-end systems
Component libraries, design tokens and Storybook teams actually use.
Performance & accessibility
Core Web Vitals audits and WCAG AA fixes with measured results.
// experience
Senior engineer
// kind words
“Teodor rebuilt our checkout in six weeks and it has not paged anyone since. Our p95 dropped by more than half.”
Lena Vos
CTO, Kova Supply