Software Developer
2025–presentTaito United Oy
Product data management software development
React
TanStack Router
GraphQL
Node.js
Postgres
Docker
Google CloudJan Härkönen
Helsinki, Finland 🇫🇮
Senior Full Stack Developer
Web apps and AI agents. Big fan of real time UIs, typesafety, performance and DX.
I'm most comfortable with
React
Go
Python
ConvexPostgres
LinuxWork and education
ReactTanStack RouterGraphQLNode.jsPostgresDockerGoogle Cloud
CEO / Software Developer
2024–2025Pion Blanc Oy
Helping small businesses navigate their massive product data pipelines and automating their sales processes
Next.jsReactPythonGoPostgres
RedisDocker
Hetzner
Software Developer
2021–2024Polycon Oy
Developing and maintaining software and databases for handling mobility aid items for Finnish hospital districts
Delphi
Microsoft SQL Server
Software Developer / Data Analyst
Feb 2020–Sep 2020Semantum Oy
LCA dashboard for environmental impact assessment
Java
InfluxDBDocker
Haskell
Research Assistant
Jun 2019–Dec 2019Aalto University School of Science
Simulating and calculating the annihilating electron-positron pair momentum density in a solid in the atomic scale using quantum Monte Carlo methods
Fortran
Quantum ESPRESSO
CASINO
CSC MahtiResearch Assistant
Summer 2018Aalto University School of Science
Semiconductor enhancement factor simulation
FortranQuantum ESPRESSOCASINOCSC MahtiMaster's degree
2018-2020Aalto University School of Science
Major: mathematics, minor: engineering physics
Exchange studies
2016-2017Korea Advanced Institute of Science and Technology (KAIST)
School of Computing
Bachelor's degree
2014-2018Aalto University School of Science
Major: engineering physics and mathematics, minor: electrical engineering
Featured projects
LINJA
2026AI-powered tool for managing live music events. Includes artist, event and venue management as well as ticket sales.
TanStack StartReactConvex
Better Auth
Resend
Railway
Stripe
Supabase
matkalla.kotimaassa.fi
2025-2026AI-powered search engine for Finnish travel destinations with customizable filters and sorting options using RAG-pipeline
TanStack StartReact
BunPythonPostgresBetter AuthRailway
TUI portfolio
2026Terminal twin of this porfolio site (ssh terminal.janharkonen.fi).
Go
Bubble TeaHetzner
SyncSpace
2025Simple list+checkbox based tool for collaborative task management with real-time synchronization
Next.jsConvex
Clerk
Vercel
PICAPI
2025API for manipulating images directly from URL parameters + platform to save own pictures in the cloud
Vanilla JavascriptPython
SQLiteHetzner
Offer generator
2024–2025Product data synchronization and sales processes automation tool as a web app aimed at small businesses
ReactPythonPostgresDockerHetznerShow all
HSL real time
2026Real-time vehicle locations for Helsinki public transport.
ReactVercel
Speed reader
2026A lightweight .epub ebook reader with RSVP (Rapid Serial Visual Presentation) capability.
ReactVercel
Wedding site
2026Wedding site to inform guests about the wedding details. Includes schedule, sign-up, and other information as well as a photo album
ReactTanStack RouterBunConvexVercel
Cloudflare R2
Secure receipt share
2026Secure way to share receipts with colleagues.
TanStack StartReactBunConvexBetter AuthRailway
Trip planner
2025Website for travel details of a 3-day trip for 60 people. Time-table, relevant links and FAQ.
Next.jsBunConvexVercel
Piggybank
2025Personal finance tracker
Next.jsConvexGo
NeonPostgres
ÉclairDB
2025Lightning-fast PostgreSQL database exploration with intuitive search and filtering capabilities
VueGo
GitHub Actions
AWS
One source of truth
2025A tool to search and filter a vast array of products blazingly fast
Next.jsGoRedis
LuaDockerHetzner
cdx
2025Bash CLI tool to cd into directories 10x faster
Bash
GitHub
Progress tracker
2025Web application to track the progress level of listed items for each user in real time using websockets
SvelteBunRedisDockerGitHub Actions
Azure
Portfolio site
2024–2026This very website. A personal full stack developer portfolio
Astro
Tailwind CSSRailway
Progress tracker
2021Mobile application progress tracker
Java
Lens and mirror simulator
2015Desktop GUI for simulating the trajectory of a laser beam through curved lenses and mirrors
Python