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Lasse Tange

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Lasse Tange

Tech Lead & Full-Stack Developer

Profile

I have spent 15 years building web and mobile applications, most of that time inside international startups and public institutions in Berlin and Copenhagen. Since 2023 I have built and launched four AI products of my own.

I am a full-stack developer who plans, architects and builds web and mobile applications end to end, with a strong grounding in TypeScript. I am equally comfortable on the frontend and the backend, working with a wide range of technologies — everything from React to PostgreSQL to the cloud.

I have worked with AI since OpenAI released GPT-3, and I have built and launched four AI products of my own — including SQLAI.ai, which is profitable and has over 150,000 users. That work covers the practical side of applied AI: RAG, embeddings and vector search, prompt design and agentic workflows.

I speak Danish, German and English.

Products

  • SQLAI.ai

    Since 2022

    AI-powered SQL multitool · Profitable

    An AI-powered SQL multitool for generating, explaining, optimising and validating SQL without losing control. It has grown from first paying customer to over 150,000 users and 25 million generated queries across 30+ database engines, including PostgreSQL, MySQL, Snowflake, BigQuery and MongoDB.

    TypeScript · React · Next.js · Astro · Node.js · PostgreSQL · LLM APIs · RAG · Stripe · Cloudflare

  • Chartmaker.io

    Since 2024

    AI charting tool

    A charting tool that accepts data in any shape, reformats it automatically and produces interactive charts from a plain-language description.

    TypeScript · React · Node.js · LLM APIs · Stripe

  • WebsiteFeedback.ai

    Since 2024

    AI feedback on landing pages

    An AI reviewer for landing pages and marketing sites. It analyses a page for clarity, positioning and UX and returns structured, actionable feedback in seconds.

    TypeScript · React · Node.js · LLM APIs · Stripe

  • ViewDiff.ai

    Since 2025

    AI-assisted diff viewer for writers

    A diff viewer for professional writers and editorial workflows. It shows original and AI-modified text side by side, so changes can be reviewed and accepted deliberately instead of trusting a black box.

    TypeScript · React · Node.js · LLM APIs · Stripe

Client work

  • alpakas.app

    Feb 2022 – May 2022

    Lead mobile & web developer · Berlin, Germany

    Architect and developer of the native mobile and web apps for a Berlin delivery startup, with end-to-end responsibility for design, structure and technical implementation.

    React Native · React · TypeScript · GraphQL

  • brandTURBO

    Nov 2021 – Dec 2021

    Contract developer · Berlin, Germany

    A short, focused development engagement for a Berlin-based company, delivered to a fixed scope.

    JavaScript · Frontend

  • Nuri (formerly Bitwala)

    Jan 2021 – Jul 2021

    React Native developer · Berlin, Germany

    Developer on the native mobile app for a Berlin crypto bank, focused on secure and comprehensible access to digital banking and cryptocurrency services.

    React Native · TypeScript · GraphQL

  • hey.car

    May 2019 – Nov 2020

    Developer & tech lead · Berlin, Germany

    A long-running engagement on Germany's first complete platform for end-to-end digital car purchases, backed by Volkswagen Financial Services and Daimler Mobility.

    React · SSR · Redux · CSS-in-JS · TypeScript · Kotlin · A/B testing

  • Wonderwerk

    Aug 2018 – Dec 2018

    Front-end developer · Berlin, Germany

    A React application for a Berlin e-learning startup, built test-first in a small product team.

    React · JavaScript · TDD · Jest · Testing Library

  • TOMCode.com

    Aug 2018

    Contract full-stack developer · Stuttgart, Germany

    An intensive delivery sprint on a web application, worked to a short, fixed deadline.

    JavaScript · Frontend · Backend

  • Danish Ministry of Higher Education and Science

    May 2016 – Apr 2018

    Freelance full-stack developer · Copenhagen, Denmark

    The longest-running of my Danish public-sector engagements. I rebuilt and redesigned ufm.dk as a fixed-price project, then designed and built the ministry's new intranet across 2017–2018.

    React · Redux · Flask · Python · MySQL · Accessibility

  • Autobranchen Danmark

    Jun 2016 – Nov 2017

    Freelance front-end developer · Copenhagen, Denmark

    The member portal for a Danish automotive trade association: member profiles and bulk member import, find-a-member search, role-based login and access control, news and event listings with custom sorting logic, calendar views and a rebuilt mega-menu.

    WordPress · PHP · JavaScript · MySQL

  • Integrationsviden.dk

    Sept 2017

    Freelance front-end developer · Copenhagen, Denmark

    Full theming and the front-end build of a Danish knowledge portal on integration research, delivered as a fixed-price project.

    PHP · JavaScript · Responsive design

  • Danish Evaluation Institute (NB-ECEC)

    Aug 2017

    Freelance front-end developer · Copenhagen, Denmark

    Design and front end for NB-ECEC, the Nordic research database on early childhood education and care, including the multilingual translation module and the editorial interface. Delivered as a fixed-price engagement.

    PHP · JavaScript · i18n · Content management

  • Danish National Board of Social Services

    Jun 2017 – Aug 2017

    Freelance front-end developer · Copenhagen, Denmark

    The front end for the agency's intranet as a fixed-price project, plus follow-up development on its practitioner forum.

    PHP · JavaScript · Responsive design

  • Forsk.dk

    Dec 2016

    Lead developer · Copenhagen, Denmark

    Sole developer on the forsk.dk web shop — architecture, implementation and launch delivered end to end as a fixed-price project.

    PHP · JavaScript · MySQL · E-commerce

  • Fritz Schur Group

    Aug 2016 – Dec 2016

    Freelance full-stack developer · Copenhagen, Denmark

    The corporate web platform for a Danish industrial group: multisite and multilingual configuration, page-builder modules, content types for products and employees, supplier and datasheet templates, search, breadcrumbs and newsletter signup — plus the mobile ordering flow for the accu-chek.guide product site.

    WordPress multisite · PHP · JavaScript · i18n

  • Danish Environmental Board of Appeal

    Dec 2015

    Lead developer · Copenhagen, Denmark

    Sole developer on nmknafgoerelser.dk, the board's public database of appeal decisions. Structured search over a large corpus of decisions with Elasticsearch, a Backbone front end against a Flask backend, and containerised deployment with Docker.

    Backbone · Flask · Python · Elasticsearch · Docker

  • Fredninger.dk

    Dec 2014 – Nov 2015

    Principal front-end developer · Copenhagen, Denmark

    Principal front-end developer on an interactive public map platform for Denmark's protected nature areas.

    JavaScript · CartoDB · SQL · Drupal · PHP · Geodata

  • Bolighed.dk

    Apr 2015 – Sept 2015

    Freelance full-stack developer · Copenhagen, Denmark

    Front-end and feature work for a Danish property marketplace: the BoligCV tenant profile editor, the SMS verification flow, polygon-based map search and ongoing front-end work.

    JavaScript · PHP · MySQL · Geodata

  • FEE.Global

    Feb 2015 – Sept 2015

    Freelance full-stack developer

    A Podio API integration and CartoDB mapping layer for an international NGO federation — data import and synchronisation, a member directory across sub-sites, test deployments and technical documentation.

    JavaScript · PHP · Podio API · CartoDB

  • Akademikernes A-kasse

    Jun 2013 – May 2015

    Freelance front-end developer · Copenhagen, Denmark

    A multi-year front-end engagement for one of Denmark's largest unemployment insurance funds. I built the job statistics web app as a fixed-price delivery, produced the interactive annual report sites for 2013 and 2014, integrated live chat, and set up analytics and A/B testing.

    JavaScript · Drupal · PHP · A/B testing · Analytics

  • Aarhus School of Architecture

    Nov 2014 – Feb 2015

    Freelance front-end developer · Aarhus, Denmark

    The front end for the school's advanced research portal and the search interface for the Pure research database — result listings, person profiles, faceted search and a search experience tuned for mobile.

    JavaScript · Drupal · PHP · Faceted search

  • The National Museum of Denmark

    Oct 2014

    Freelance front-end developer · Copenhagen, Denmark

    The front end for the museum's online collections browsing: media slider, infinite scroll and full-screen slideshow, tuned for mobile, on top of Angular, Express and Elasticsearch.

    Angular · Express · Elasticsearch

  • Sammen om Motion

    Apr 2013 – Jun 2014

    Freelance full-stack developer · Copenhagen, Denmark

    A Danish community platform for group exercise. Team and group system with role-based coordinator permissions, member galleries, a shared calendar, comment threads, SMS and email notification preferences, signup and contact forms, plus the whole responsive layer and the rollout to production.

    Drupal · PHP · JavaScript · Responsive design

  • Cykelsuperstier

    Sept 2013 – Oct 2013

    Freelance front-end developer · Copenhagen, Denmark

    Front-end and integration work on the route platform for the Greater Copenhagen cycle superhighway network: ibikecph route maps and service-station data wired into the Drupal backend, route description display, and optimisation for mobile and tablet.

    JavaScript · Drupal · PHP · Mapping APIs

  • Additional clients

    2013 – 2018

    Freelance developer · Copenhagen, Denmark

    Shorter engagements and maintenance across the same period: Socialministeriet, Mødrehjælpen (analytics), Hans Buch & Co, XO Shipping, V.DK, AT Work and Tommy V.C — plus a commercial SiteAttention plugin for WordPress delivered as a fixed-price project.

    WordPress · Drupal · PHP · JavaScript · Analytics

Technologies

  • AI

    • LLM APIs (OpenAI, Anthropic)
    • RAG and vector search
    • Embeddings and semantic search
    • Prompt engineering
    • AI-assisted development (Claude Code, Codex CLI)
    • Applied AI product design
    • Agentic AI workflows

  • Frontend

    • React and React Native
    • Next.js and Astro
    • Tailwind CSS and design systems
    • State management (Redux, Zustand, Nanostores)
    • SSR, SSG and web performance
    • Accessibility and cross-browser compatibility
    • SEO and web analytics

  • Backend and data

    • Node.js
    • REST and GraphQL APIs, typesafe end to end
    • PostgreSQL, MySQL and Redis
    • Data modelling and ORMs (Prisma, Drizzle)
    • Elasticsearch and search
    • Geospatial data and mapping
    • Payments and integrations (Stripe, Lemon Squeezy)

  • Programming languages

    • TypeScript
    • JavaScript
    • SQL
    • Python
    • PHP

  • Testing and tooling

    • Testing (Jest, Testing Library, Playwright)
    • Test-driven development
    • Storybook
    • Monorepos and modern tooling (pnpm, Vite, Rspack)
    • A/B testing and feature flags

  • Platform and delivery

    • CI/CD (GitHub Actions)
    • Docker
    • Cloudflare, AWS and Vercel
    • Linux, Nginx and VPS
    • Git

  • Product and leadership

    • Product strategy and digital business
    • Team leadership and mentoring
    • UX research and user testing
    • Domain-driven design
    • Online marketing and growth

Open source

  • rshono

    A minimalist web framework built on Hono, Rspack and React Server Components, with an explicit API and no file-system routing conventions. This site runs on it.

  • Sublime ES7 React/Redux snippets

    A popular snippet package for ES7, React, Redux and React Native in Sublime Text — both JavaScript and TypeScript.

  • flask-reactjs

    A Flask, React/Redux and webpack boilerplate, so a new project starts from a working setup rather than an empty directory.

  • flask-scaffolding

    Flask scaffolding featuring SQLAlchemy, Backbone and Sass.

  • react-collapse-simple

    A small library for collapsing and expanding content with a sliding animation, written in TypeScript.

  • react-simple-social

    Every social share link through one simple, lightweight React component.

  • git18n-node

    A lightweight npm package that abstracts translation management away from the developer.

  • Browser lookup extensions

    Quick dictionary and translation lookups straight from the browser — one extension each for DeepL, Langenscheidt and Ordnet.

Languages

  • Danish — Native speaker
  • English — Full professional proficiency
  • German — Full professional proficiency

Education

Copenhagen Business School — Business Administration and Computer Science.