CV
Senior Full-Stack Engineer – TypeScript / React / Node.js
Berlin, Germany | | post@stefanwille.com
Website | LinkedIn | GitHub
Available … | Remote or Hybrid (Berlin) | Contract
Summary
Senior full-stack engineer specializing in TypeScript, React, and Node.js, with 30 years of professional experience. I work closely with product owners and designers to decide what to build, then build features end to end: data model, API, and UI. I build web applications with LLM integration and work with agentic coding tools (Claude Code, Cursor).
I started in 1996 at NETLIFE, building online banking systems in C++ and Java, and became VP of Research & Development, staying through the company's IPO. Later I co-founded two companies as CTO — Balao (sold to Fyber in 2010) and Papersmart. My stack moved from C++ to Java EE, then Ruby on Rails, and today TypeScript, React, and Node.js. Freelance since 2002, with two founder stints in between, based in Berlin.
Own Projects
- Billet (2026) – CLI coding agent built directly on the Anthropic SDK: agentic loop, bash and text editor tools, sandboxing, plan mode, skills, eval suite (TypeScript, Bun)
- Smart Rename (2025) – AI-based desktop app that extracts invoice metadata and auto-renames files (Vercel AI SDK, Evalite, Tauri, TypeScript, React)
- Recto (2026) – Published web tool for planning book page layouts, in production use on a 400-page book project (TypeScript, React, Supabase)
- Anki MCP Server (2026) – lets LLMs generate and correct flashcards (TypeScript)
- crystal-redis (2015) – Redis client library (Crystal)
Experience
Parloa – AI-based Contact Center Platform
03/2025 – 12/2025 | Frontend Platform Developer | TypeScript, React
Parloa's product offers AI-based contact center agents for customer service.
I designed and implemented a server-driven UI (SDUI) package, enabling backend developers to declaratively build UIs for their services without depending on frontend developers.
- Evaluations system
- GPT-5 integration
- Multi-agent orchestration
- UI component library
Built primarily using agentic AI (Claude Code, Cursor).
I worked in a 10-person frontend platform team. Parloa is a scaleup with 300+ people and a $3 billion valuation. Their customers include Booking.com, American Express, Generali, Allianz, and TUI.
Next Logistics Ventures – seabo
10/2022 – 04/2024 | Lead Full-Stack Developer | Node.js, NestJS, React
seabo is a SaaS marketplace for chartering cargo ships.
The software ran on a legacy PHP backend, which had become the main bottleneck for development.
- Add a modern backend stack as the foundation for new features and a gradual migration off PHP
- New features
- Scoped features with the project manager
- Introduced TypeScript and the NestJS framework for the backend
- Selected core backend technologies (OpenAPI / REST, BullMQ, TypeORM)
- Data model design
- Added code generation from OpenAPI specs
- Led the frontend and fullstack developers
- Scoped and built the vessel database and Stripe subscription billing end to end
- Extended the chartering marketplace
- Rebuilt realtime updates with socket.io
ISV (Confidential) – SaaS Product
07/2020 – 09/2022 | Lead Frontend Developer | TypeScript, React
Development of a Software-as-a-Service (SaaS) product.
The frontend was a 7-year-old JavaScript React codebase. Technical debt had slowed development down and QA depended on a slow E2E test suite.
- Reduce technical debt
- Improve quality
- New features
- Migrated the frontend codebase from JavaScript to TypeScript
- Replaced hand-built components with an industry-standard component library
- Modernized the code to use current React patterns
- Introduced automated tests, raised quality and improved velocity
- Delivered new features alongside the modernization
- Led and coached a 4-person frontend team
Zalando – Procurement Portal
09/2019 – 03/2020 | Lead Frontend Developer, Coach | TypeScript, React
Zalando is Europe's leading fashion e-commerce store.
This greenfield project replaced Zalando's existing procurement platform. The portal supports roughly €1 billion in annual fashion product purchases.
- Project setup
- Feature development
- Helped scope the product with the product owner and UX designer
- Selected frontend technologies
- Designed frontend architecture
- Coached 4 developers in the technologies used
- Taught workshops about React and MobX
- Worked in a cross-functional team of 12, including 9 developers
DMG – Dentamile Connect
01/2019 – 08/2019 | Frontend Developer | React, Node.js
In this project the customer developed a SaaS for the digital, personalized production of dental products such as crowns and bite splints through browser-based CAD/CAM. A dental laboratory or dentist can digitally scan the patient's jaw. Based on the jaw's model, the user specifies the desired product in a web browser in a CAD component in 3D, which uses WebGL. The individual steps are determined and sequenced by a workflow mechanism. Once finished, the user prints the design using a special dental 3D printer. The end product is directly usable by the patient.
- Establish best practices
- Feature development
- Built relationships with partner companies
- Designed, negotiated, and implemented the API between the SaaS and the WebGL CAD component built by a partner agency
- Set up the UI component library
- Coached other frontend developers
Intersection – IxNTOUCH
10/2018 – 12/2018 | Frontend Developer | React
Intersection is an Alphabet investment. They are active in the AdTech space, where they make interactive kiosk systems with touch screens for public spaces, including train stations, airports, shopping malls and streets. In this Smart City engagement, I developed the maps functionality for the kiosk software and supported the production rollout with CTA (Chicago Transit Authority), the public transport provider in Chicago.
Equal Experts – Associate CRM
09/2018 – 10/2018 | Full-Stack Developer | Node.js, React
Development of a small CRM which the customer uses to track the availability of their associates.
ISV – Manufacturing Project
04/2018 – 05/2018 | Frontend Developer | React
Development of a Software-as-a-Service (SaaS) product in the manufacturing space.
HRS Innovation Lab – HRS
04/2017 – 03/2018 | Full-Stack Developer, Coach | React, Node.js
HRS runs a set of websites for hotel bookings as a result of their acquisitions. The job of our team was to develop a common platform that would unify all the existing brand websites as well as build the new hotel.de web application. I worked on both the React frontend as well as the Node.js backend. Part of my responsibilities was coaching other frontend team members.
Jobkraftwerk – Jobkraftwerk Phase 2
01/2017 – 01/2017 | Frontend Developer | React
I helped out while this existing customer worked towards a new milestone.
Movinga – Movinga
06/2016 – 12/2016 | Full-Stack Developer | Ruby on Rails
Movinga offers removals in several countries and acts as an agent between the end customer and the partner company. I helped Movinga to digitize their business with internet technology. Specifically, I was involved in the migration from their old web application to a new Ruby on Rails platform, which had deep integration with Salesforce CRM. Also, I helped to improve the Scrum implementation, coached team members and performed many code reviews.
During a one-week hackathon, together with a small team, I reimplemented substantial parts of the native Android partner app in React Native on iOS.
I also set up the project for the reimplementation of the inventory client with React and Redux and participated in the implementation of its initial features.
Jobkraftwerk – Recruiting Software
03/2016 – 05/2016 | Lead Frontend Developer, Scrum Master | React
Jobkraftwerk supports refugees in finding jobs with the help of their web application. I helped to structure the project as a Scrum master. Also, I led the development team and worked on the frontend. The frontend was designed mobile first and communicated with the backend using a REST API.
Nokia HERE – Product Operations Tools
08/2015 – 12/2015 | Lead Backend Developer | Ruby on Rails
I extended an existing application that HERE uses to manage the localization process of all HERE applications into over 100 languages, set up the API, improved the Scrum implementation, helped with staffing, coached new and existing team members, managed the production system, and acted as the interface to the central IT department.
AKINGO – SaaS
07/2015 – 08/2015 | Backend Developer | Node.js, Express, Lua
Developed a CMS content customization and personalization server.
Tuttle – Tuttle
11/2014 – 01/2015 | Full-Stack Developer | Ruby on Rails
Filming for a movie produces a lot of metadata that is very important for the post-production process. Tuttle centralizes this metadata in a cloud solution and makes it available for an efficient workflow.
Fyber – Ad-Server
04/2014 – 10/2014 | Team Lead, Backend Developer, Scrum Master | Ruby on Rails
Fyber is a technology provider that helps mobile publishers monetize their content on mobile devices through targeted advertising. At Fyber I led a scrum team for the advertiser side of the business. Later I moved into the Scrum Master role. The team consisted of 8 people (5 developers, 2 QA, 1 product owner) and worked on backend features.
Consumerise – SaaS Vertical Solution
11/2013 – 03/2014 | Backend Developer | Ruby on Rails
In this project I helped the customer to develop a SaaS-based administrative solution in the health sector. My work was in the backend. The most interesting aspect was the semantic search feature.
SAP – Redmine Customization
09/2013 – 03/2014 | Backend Developer | Ruby on Rails
For SAP I developed plugins for the project management software Redmine, with the objective of improving its functionality and usability.
Papersmart – Marketplace
09/2010 – 05/2013 | CTO, Co-Founder | Ruby on Rails
With some colleagues I co-founded Papersmart, a B2B price comparison web app for stationery. I also served as their CTO.
I was involved in all technological and product aspects of the application. These included the marketplace, price comparison, SEO, analytics, administration back office, payment, billing and the REST API for suppliers.
Balao – GratisPay
04/2009 – 02/2010 | CTO, Co-Founder | Ruby on Rails
As CTO and co-founder at Balao GmbH I was responsible for everything related to technology. I hired the development team, introduced the development process (Scrum), selected the technology platform (Ruby on Rails) and the production platform (Amazon AWS), led the team, gathered and defined requirements, designed the architecture, built important parts of the software, and organized quality assurance.
BizSphere – Sales Enablement
11/2006 – 03/2009 | Team Lead Backend | Java, Spring, Hibernate
Led the backend team and shaped the architecture of this sales enablement product, deployed at Nortel and IBM. Worked across teams in Germany and China.
O₂ – Prepaid Customer Portal
05/2006 – 09/2006 | Backend Developer | Java, Spring, Hibernate
Developed the customer portal's middle tier and rebuilt its prepaid section, using TDD.
PPI – EBICS Payments Server
12/2005 – 03/2006 | Backend Developer | Java, Spring, Struts
Built payment use cases and evolved the Hibernate/Spring persistence layer used by a 40+ developer team, coaching the team on it.
PPI – Sales Intelligence for Savings Banks
06/2005 – 11/2005 | Backend Developer | Java, IBM Websphere
Designed and built the rule engine, including a compiler translating a domain-specific language into Java bytecode.
Kühne+Nagel – Tender Management
09/2004 – 04/2005 | Backend Developer | Java, Spring, Hibernate
Built a tender processing system for geographically distributed teams.
Reuters – Portfolio Management System
01/2002 – 08/2004 | Analyst, UI Developer | Java, Swing
Designed and built the asset allocation functionality.
Self-funded – HBCI Server
07/2000 – 03/2001 | Backend Developer, Founder | Java, EJB
Built an HBCI server for retail banking.
NETLIFE – Online Banking
01/1996 – 05/2000 | VP Research & Development | C++, Java
Architected and built internet banking servers and clients for German banks including Commerzbank and Postbank. Headed a department of 10 developers. Supported technical due diligence for the company's IPO.
Publications
I have written two books:
- 2006 – Book "Spring und Hibernate – Eine praxisbezogene Einführung", Oates, Langer, Wille, Lueckow, Bachlmayr; second edition 2008 / Hanser Verlag
- 2001 – Book "Go To Java Server Pages", Stefan Wille / Addison Wesley
Education
Bachelor's degree, University of Hamburg:
- Major in computer science (distributed systems)
- Minor in business economics
2006 CSM – Certified Scrum Master
Languages
- German: Native speaker (C2)
- English: Fluent (C1)
- Italian: Beginner (A2)
Volunteer Work
- Mentored a junior developer, 11/2020–03/2022
- Mentored a junior developer, 03/2017–12/2017
- OpenTechSchool workshops as coach – https://www.opentechschool.org/
- Hackership program as coach – https://www.hackership.org/
- RailsGirls workshops and project group as coach – https://railsgirls.com/
Hobbies
- Argentine Tango
- Learning Italian
- Fitness