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Lasse Tange

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Lasse Tange

Senior Full-Stack Developer & Tech Lead

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.

I am a full-stack developer who plans, architects and builds web and mobile applications end to end, primarily in TypeScript/Node.js. I am equally at home on the frontend and the backend, working with a wide range of technologies and languages.

Beyond development, I am also experienced in setting up, scaling and operating web applications: cloud infrastructure, Infrastructure as Code (IaC), CI/CD pipelines and testing.

I have also worked with AI since OpenAI released GPT-3, and I have built and launched several AI products of my own. In that work I use a range of AI technologies: RAG, embeddings and vector search, prompt design and agentic workflows.

Products

Four products I have taken all the way myself: idea, architecture, UX, operations, marketing and revenue.

  • SQLAI.ai

    2022 – Sept 2026

    AI-powered SQL multitool · Profitable

    An AI-powered SQL multitool for generating, explaining, optimising and validating SQL without losing control. It has grown from the first paying customer to over 150,000 users across 30+ database engines.

    TypeScript · React · Next.js · Node.js · PostgreSQL · LLM APIs · RAG · Payments · Cloudflare · IaC

  • Chartmaker.io

    2024 – May 2026

    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 · Payments · Cloudflare · IaC

  • WebsiteFeedback.ai

    2024 – May 2026

    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 · Payments · Cloudflare · IaC

  • ViewDiff.ai

    2025 – May 2026

    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 · Payments · Cloudflare · IaC

Client work

A decade of client work, first freelancing in Copenhagen and later inside the German startup scene.

  • 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 · UI/UX · TypeScript · GraphQL · Node.js · AWS · IaC · Payments

  • brandTURBO

    Nov 2021 – Dec 2021

    Contract developer · Berlin, Germany

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

    TypeScript · Frontend · Node.js

  • 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 · UI/UX · GraphQL · Node.js · AWS · IaC · Solarisbank

  • 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 · Redux · UI/UX · TypeScript · Kotlin · Node.js · IaC · AWS

  • 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 · Node.js · Heroku

  • TOMCode.com

    Aug 2018

    Contract full-stack developer · Stuttgart, Germany

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

    TypeScript · React · Node.js

  • 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 (e.g. GitHub Actions)
    • Docker
    • Cloudflare, AWS and Vercel
    • Linux, Nginx and VPS
    • Git
    • Infrastructure as Code (IaC)

  • 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.