Project Profile
Sebastian Fastner
Senior React & TypeScript Developer · Frontend Architect
Profile Summary
Hands-on frontend architect and senior React/TypeScript developer with more than 20 years of project experience. Builds and modernizes international platforms in banking and asset management, e-commerce, and enterprise SaaS – from component architecture and testing to CI/CD and cloud migration. Particularly effective in demanding product and transformation phases where architectural decisions and hands-on delivery need to come together.
Full Consultant Profile: sebastian-consulting.com/fastner
Available immediately (as of September 2026)
Full-time
Engagement via Sebastian Software GmbH
Remote-first; occasional on-site work throughout Germany, Austria, Switzerland, and the Benelux. More distant locations by arrangement.
Technical Focus
- React
- TypeScript
- Next.js
- Node.js
- GraphQL
- Testing
- CI/CD
Direct Contact
- s.fastner@sebastian-software.de
- Phone
- +49 176 32042696
- Location
- Mainz, Germany
- Languages
- German and English
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Senior React & TypeScript Developer · Frontend Architect
Selected Project Experience · Fintech & E-Commerce
DWS / MorgenFund · Investment Management Platform
Senior Frontend Architect · 10/2020 – 07/2024
Long-term development of an international investment management platform as Senior Frontend Architect.
- Implemented the migration to Azure and a continuous deployment strategy.
- Ported a React dashboard to React Native, covered it with Jest and React Testing Library, and rolled it out to additional European and Asian markets.
React, React Native, TypeScript, Azure, Continuous Deployment, Jest, and React Testing Library
Witt-Gruppe (Otto Group) · Multi-Brand E-Commerce Platforms
Senior Frontend Architect · 04/2019 – 09/2020
Led the frontend rebuild for the Witt Group within the Otto Group.
- Established the technical foundation for 17 multi-brand online shops across international markets.
- Built a Next.js/React/TypeScript frontend, an Apollo GraphQL layer, and automated test infrastructure.
Next.js, React, TypeScript, Apollo GraphQL, Contentful, AWS, and Kubernetes
DWS (Deutsche Bank) · Robo-Advisor Investment Platform
Senior Frontend Architect · 04/2016 – 03/2019
Built the WISE white-label investment platform for more than ten European and Asian investment portals.
- Delivered from sales prototype through to a production white-label robo-advisor.
- Owned a React/TypeScript component library, REST integration, and CI/CD on Microsoft Azure.
React, TypeScript, Vue.js, Spring Boot, Keycloak, DocuSign, and REST API
Project Profile · 2 / 5
Senior React & TypeScript Developer · Frontend Architect
Selected Project Experience · Enterprise SaaS & Internationalization
Regrello · AI-Powered Internationalization
Senior Technology Consultant · 10/2024 – 09/2025
Near-real-time internationalization of an enterprise SaaS platform using React, TypeScript, Go, GraphQL, encrypted Temporal workflows, and AI-assisted translation.
- Translated new and changed content within seconds using an event-driven workflow, prioritizing participants' native languages before rolling out to all available languages.
- A one-off on-site assignment in the US demonstrates willingness to travel internationally.
React, Go, GraphQL, Redis, Temporal, Google Gemini, and TypeScript
Recent Hands-on Products
Terminaro · Product by Sebastian Software GmbH · SaaS · Appointment Booking System
Product Engineer · 01/2026 – 08/2026
Multilingual appointment scheduling system with a public booking page and integrated administration.
- Implemented public booking, administration, calendar integration, email delivery, and secure deployments.
- Used React Router, TypeScript, Convex, and automated tests as an end-to-end product stack.
React Router, Convex, TypeScript, Better Auth, CalDAV, and Bunny.net
Palamedes · Product by Sebastian Software GmbH · Dev Tools · AI-Powered Localization Platform
Product Architect · 10/2025 – 06/2026
Developer-first platform for AI-assisted localization within Git and release workflows.
- Designed and implemented a CLI-first workflow, translation pipeline, QA reports, and terminology features.
- Delivered the website, newsletter backend, authentication, and API and pipeline infrastructure.
AI Applications, Localization, React Router, Convex, TypeScript, Lingui, and Relanto
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Senior React & TypeScript Developer · Frontend Architect
Further experience · complete career history
- 2016Deutsche Telekom · Senior Application Architect
- 2015–2016Jako-o · Lead Application Architect
- 2015Deutsche Telekom · Lead Application Architect
- 2014Suzuki Deutschland · Fullstack UI Architect
- 2014Deutsche Bank · Frontend Developer
- 2010–2013Deutsche Telekom / Tolino‑Allianz · JavaScript Developer
- 2010–2013Deutsche Telekom · JavaScript Developer
- 2010Deutsche Telekom · Mobile Developer
- 2008–2009Deutsche Telekom · Frontend Developer
- 2007–20083ado AG · Java Fullstack Developer
- 2006–2007netz98 · Frontend Developer
- 2006Commerzbank · Java Developer
- 2006Creative Communications · PHP Developer
- 2004–2008DoubleF IT · Founder & Managing Director
- 2002–2005Technische Hochschule Bingen · IT System Administrator
- 2000–2001Boehringer Ingelheim · Software Developer
Education, Languages & Contact
- Degree
- Diplom-Informatiker (FH) – German diploma in computer science
- s.fastner@sebastian-software.de
- Phone
- +49 176 32042696
- Location
- Mainz, Germany
- Languages
- German and English
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Sebastian Software GmbH
Dalheimer Straße 12
55128 Mainz
Amtsgericht Mainz HRB 45232
USt-IdNr. DE295226721
info@sebastian-software.de
www.sebastian-software.de
This profile may be shared, used, and stored for project inquiries and proposals.
As of: September 4, 2026
© 2014–2026 Sebastian Software GmbH
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