Münster, DE · June 2026
Software Engineer · Founder · Managing Director
Tristan
Zellner.
10+ Years Engineering LeadershipRuby on Rails Münster
Clarity, simplicity and drive. As a Software Engineer, CTO and now as a founder, I build products, teams and structures that work.
Tristan Zellner 2025
01What matters to me
Clarity, simplicity and purposeful work are fundamental principles for me. Alongside this, a friendly working relationship matters – even in difficult project situations – without shying away from clear, open and sometimes critical words.
01
Clarity
Clear structures, plain language, transparent decisions.
02
Simplicity
Reduce complexity, distil the essentials, execute with focus.
03
Drive
Work consistently towards results. Pragmatic, not dogmatic.
04
Collaboration
Friendly communication even in difficult situations, without shying away from critical words.
02Experience
Nov 2024 ↓ present Full-time
Founder & Managing Director
travelbuddy — Münster — ↗ travelbuddy.techAll-in-one platform for professional group travel operators – accommodation, bookings, participants and invoices in one place.
- Fullstack Ruby on Rails application for managing group travel
- Independent conception, design, process development and implementation
- Customer workshops and requirements analysis for customisation and further development
- AI-assisted development with Claude Code and Cursor
- CI/CD, operations, backup and maintenance
Jul 2022 ↓ Aug 2024 Full-time
CTO / Head of Software Development
finstreet — Münster — ↗ finstreet.deLeading software development as technical and strategic sparring partner to executive management.
- Strategic alignment of technologies, personnel and processes
- Building an internal development team – hiring, onboarding, internal structures
- Managing external service providers including quality management and crisis intervention
- Personnel responsibility for up to 15 people – 1:1s, development, salaries
- Acquisition and sales meetings as technical contact
Jun 2018 ↓ Jul 2022 Full-time
Software Engineer
finstreet — Münster — ↗ finstreet.deFull-stack development and technical product owner for several banking and finance products.
- Development of digital application processes for banking products
- Technical Product Owner – interface between business and development
- REST API development for a financial analysis product using Ruby on Rails
- Refactoring a fullstack Rails application into an SPA/API architecture (Rails + React + React Native)
- Leading a team of up to 15 developers on a multi-tenant SaaS application
- Modularisation and refactoring of legacy code
— Education
Feb 2016 – Apr 2018 Working Student · Java Development Fiducia & GAD IT AG
2014 – 2018 Bachelor of Science · Computer Science FH Münster
Sept 2007 – Feb 2010 Apprentice · IT Systems Specialist Deutsche Telekom
03Selected successful projects
from 2024
Founding and development of travelbuddy
- Complete conception and new development of software for managing group travel for SMEs
- Development of processes and design
- AI-assisted development with Claude Code and Cursor
- Deployment and operation on self-managed virtual private servers
- Coverage of the complete software development lifecycle
from 2022
Leading a multi-tenant SaaS in banking
- Leading a team of up to 15 developers on a multi-tenant software-as-a-service application
- Roadmap planning and staffing capacity management
- Refactoring legacy code and modularising components to improve multi-tenant capabilities
- Participating in acquisition and sales meetings as technical contact
- Requirements and implementation management with clients
2021
Leading an architecture refactoring project
- Refactoring a fullstack Ruby on Rails application into an SPA/API architecture (Rails backend + React frontend + React Native mobile)
- Complete planning and management of the refactoring project including active backend development
since 2018
Various Ruby on Rails projects
- Backend and fullstack development for various clients and products
- Development and maintenance of REST APIs
- Integration of various external APIs and third-party services
- Test Driven Development (TDD)
- CI/CD pipelines and independent operations
04Skills
01 Leadership
Team BuildingHiring & Onboarding1:1 & FeedbackStakeholder Management
02 Product & Process
Technical Product OwnerRoadmap PlanningRequirements ManagementAcquisition & SalesCrisis Intervention
03 Backend
Ruby on RailsREST APIsPostgreSQLMulti-Tenant SaaS
04 Frontend
HTML / CSSJavaScriptHotwire (Turbo/Stimulus)
05 AI-Assisted Development
Claude CodeCursor
06 DevOps & Tools
DockerLinuxKamalresticCI / CD
05Personal
I'm a down-to-earth, active guy from Münster who has been playing football since childhood. Teamwork and a performance mindset go hand in hand for me. In summer, I'd rather pitch a rooftop tent in nature than fly to a hotel ;)
01
Sport
Balance, discipline, routine
02
Football
Teamwork, creativity, fun
03
Camping
Nature over resorts
06Contact
Looking for a Product Engineer, Head of Engineering or CTO?
Location
Münster, Germany
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