Daniel
Dunderfelt
Freelance Full-Stack Developer · Helsinki, Finland
I'm a freelance full-stack developer from Helsinki, Finland. I specialise in building top-quality applications from scratch to production, across web, mobile and the servers and APIs behind them.
I can work with most languages and technologies, but I'm most experienced with TypeScript and React. For mobile I do my best work with Expo and React Native, and for server-side and API services I reach for Node.js (or alternatives like Bun).
I'm particularly focused on making the user experience delightful, accessible and intuitive. I'm not afraid to dive into languages and frameworks that are new to me, and I choose what's best for the task at hand. I've worked across eCommerce, healthcare, critical infrastructure, entertainment, logistics and real estate, and I approach every project with curiosity and an eagerness to solve problems.
A decade of shipping real products
- 2024–Present
Architect & Lead Developer
Aikoa Intentions Oy
Selected for the Antler Nordic 7 cohort in Helsinki, a three-month startup residency at VC firm Antler. The result is Aikoa, a service reinventing the private real-estate market. I built the first MVP in a few months with Next.js and the Vercel AI SDK: smart AI integrations, rich 3D maps, Stripe payments, App Router and React Server Components. A second, React Native (Expo) app follows, piloted via Expo web and shipped to the stores from the same codebase.
- 2020–Present
Founder & Full-Stack Developer
Dunderfelt Consulting Oy · Freelance
My own limited company and the vehicle for my freelance work. Through it I've built products for Finnair, HUS, HSL, Fingrid, Relex, A-lehdet and more, from offline-first mobile apps to critical grid infrastructure. I frequently act as lead developer, keep releases on track under pressure, and mentor the teams I join.
- 2021–Present
Founder
Dunderfelt Digital Oy
Founded to build a mobile app with my father, psychologist and author Tony Dunderfelt. We also produce audio-visual work for clients and recently published a well-received 16-part video course on intuition.
- 2018–2020
Full-Stack Developer
Freelance Developer · Sole Proprietor
Went freelance at the start of 2018, building a customer-service portal for A-lehdet and then joining a multi-disciplinary agile team at HSL. Deepened my repertoire with complex apps built on TypeScript, PostgreSQL and Azure.
- 2013–2018
Developer
Mirum Agency (ActiveArk JWT)
Started as a developer trainee and grew into a developer over almost five years, as ActiveArk JWT became Mirum and part of a global agency network. Worked with clients like Neste, Nokia, Finnair, Holvi, Lassila & Tikanoja and Nordea, from promotional sites and HTML5 to full web apps, WebGL games and eCommerce. This is where I became full stack, and ready for anything.
A closer look at what I've built
Finnair Mobile App
Mobile DeveloperThe new Finnair native app (Expo / React Native) for iOS and Android, serving every stage of the customer journey: flight booking, ancillaries and loyalty. Offline-first with a local SQLite database syncing to multiple APIs, extensively tested with Maestro, and shipped through EAS Build, OTA updates and CI Workflows.
Aikoa
Architect & Lead DeveloperTwo apps: a Next.js MVP and a React Native (Expo) mobile app, both with AI integrations via the Vercel AI SDK. Full-stack, from delightful UI and animations down to low-level database tuning, auth, server-side logic, durable workflows and LLM operations. I also fine-tuned and deployed a custom embedding model for the project.
HUS Omapolku
Lead DeveloperThe flagship mobile product of HUS, the public healthcare provider for the Helsinki region. A React Native app built to healthcare standards: strong authentication, accessibility, sensitive-data security, multiple languages, secure API integrations, and a wealth of interactive multimedia content.
Relex Mobile Replenishment
Mobile DeveloperMORE, an offline-first React Native (Expo) app for retail store staff. Built with a local SQLite database and sync engine, end-to-end tested with Maestro, and shipped via EAS. I made the data sync over 10× faster and acted as lead developer, mentoring the team and keeping releases on track.
Fingrid Grid Applications
Architect & DeveloperInternal applications critical to the Finnish electricity grid, producing and consuming data over Kafka. I used Kotlin and Kafka Streams to build part of an application, and helped design common libraries and processes on Azure and Kubernetes.
HSL Reittiloki & Bultti
Architect & DeveloperReittiloki stores second-by-second public-transport vehicle data to ensure service quality; Bultti tracks operator contract compliance. Built with React, TypeScript, GraphQL, Node.js, Leaflet, Postgres/Citus and Redis.
Escape Room Helsinki
Architect & DeveloperAn eCommerce and booking storefront where most customers reserve and pay for games, with an integrated staff scheduling system that turns each booking into a work shift. Built on WordPress and WooCommerce with custom plugins and a React front end.
This is a selection, not the whole list. There's plenty more, plus countless unreleased side projects of my own.
See what I'm buildingTechnologies I build with
Languages & Runtimes
- TypeScript
- JavaScript
- Node.js
- Bun
- Deno
- Kotlin
- PHP
- SQL
- HTML5
- Python
Web & Frontend
- React
- Next.js (App Router, RSC)
- TanStack Start
- TanStack Query
- TanStack Router
- Vite
- SSR
- Tailwind
- CSS / SCSS
- Framer Motion
- WebGL / Three.js
- Radix / shadcn/ui
- Accessibility (a11y)
Mobile
- React Native
- Expo
- EAS (Build, OTA, CI)
- App Store releases
- Offline-first & sync
- On-device SQLite
- On-device AI models
- Maestro E2E
AI
- LLMs (Claude, GPT, Gemini)
- Agentic development
- Cursor (top 0.2%, 2025)
- Vercel AI SDK
- RAG & embeddings
- Vector DBs (pgvector, Qdrant)
- Local models
- OCR & document ingestion
- Fine-tuning & deployment
Backend & Data
- PostgreSQL (pgvector, PostGIS)
- GraphQL / Apollo
- tRPC
- Hono / Elysia / Express
- Prisma / Drizzle
- Supabase
- SQLite (fts5, tuning)
- Kafka
- Workflows & task queues
- Convex
DevOps & Infra
- Vercel
- Cloudflare
- AWS
- Azure
- Google Cloud
- Apple Developer / App Store Connect
- GitHub Actions & Workflows
- Docker / Kubernetes
- SST
- Feature flags
- Observability (Datadog, PostHog)
Beyond code
Toastmaster since 2022, and President of the Stadi Talkers club for the 2024–2025 season, plus talks at meetups and internal events, with an appetite for more.
Photography is my main hobby outside of programming, with extensive stills experience and some video production (audio, lighting and editing) through Dunderfelt Digital.
Languages
- EnglishFluent
- FinnishNative
- SwedishFluent