Fractional .NET Architecture

by Janis Pütz

Your .NET system should get lighter as it grows — not heavier.

I'm Janis Pütz — fractional .NET architect. I design architecture and build it too: all the way into production, with tests, monitoring, and AI-augmented delivery. 50% capacity, split as needed, remote-first.

SaaS PlatformsC#.NET 10Blazor Clean ArchitectureDDD / CQRSAI-augmented
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CARIAD (Volkswagen Group)License management system shipped on Clean Architecture (ports & adapters).
DMS GreenfieldDocument management system architected from day one — ~80% test coverage as the daily standard.
Agri-robotics SaaSDomain model reworked: one codebase, two products.
Janis E. H. Pütz

How I work

Ownership into production. Whoever decides the architecture is accountable for it all the way into production. So I don't just design — I implement, test, deploy, and watch the system run.

AI in concrete terms, not buzzwords. A nightly Claude Code error triage opens pull requests for human review; weekly infrastructure trend analyses become issues. AI tools accelerate my work — accountability stays with me.

Test discipline. xUnit, bUnit, and Playwright are the standard; TDD where it pays off — and honestly, not where a UI prototype will look different again tomorrow.

Why fractional?

Many product and SaaS teams need architectural seniority but can't justify a full-time architect. That's exactly what my model is built for: 50% capacity, split as needed, remote-first. You get architecture decisions, reviews, and implementation from one person — continuously across your system's lifecycle, not as a one-off consulting engagement.

My own products

I operate what I build: my booking SaaS buchungsnest.de runs in production with external customers — on an event-sourced core, with its own CI/CD pipeline including staging and smoke tests, plus OpenTelemetry monitoring. Every recommendation I make as an architect has survived my own operations first.

That includes GDPR-compliant erasure via crypto-shredding: personal data is encrypted per person; erasure destroys the key while remaining provable in the audit log itself. At the same time, the system respects German statutory retention periods for invoice data. Privacy and auditability aren't opposites — if the architecture plans for both from the start.

13+ years of architecture and development experience

C# & .NET in production since 2013
  • C# 14
  • .Net 10
  • ASP.Net Core
  • Entity Framework Core
  • UI: Blazor (Server & Hybrid) & Razor Pages
  • .NET MAUI
  • SignalR
Master of Science in Information Systems
  • Studies at the University of Osnabrueck, Germany 2007 - 2012
  • Bachelor of Science in Information Systems (2011)
  • Master of Science in Business Informatics (2012)
  • Semester abroad at the University of South Florida (2009)
  • Integration of complex applications in ETL processes of data warehousing (2011)
  • Use of artificial neural networks for cloud computing (2011)
  • Conception and prototypical implementation of a meta-operator for the application and evaluation of alternative classification methods for the open source data mining tool RapidMiner (2012)
Experience in software architecture
  • Clean Architecture
  • Design Patterns
  • API-Design
  • DDD (domain driven design)
  • TDD (test driven development)
  • DRY - Don't repeat yourself
  • SOLID principles
  • Single-Responsibility
  • Open-closed principle
  • Liskovsche Substitution
  • Interface-Segregation
  • Dependency-Inversion
  • CQRS (Command-Query-Responsibility-Segregation)
  • Hexagonal architecture (ports and adapters)
Since 2024: Nature Robots (robotics)
  • Employed since October 2025 (freelance since Nov 2024) — 50% permanent, 50% free for select freelance projects
  • Reworked the domain model (decoupled Environment from Robot) so one codebase ships as both the fleet-management platform and a standalone planning SaaS
  • Designed and delivered an internal AI-Engineering Enablement program: tool/vendor evaluation, EU data-residency/training-data compliance matrix (Claude, Copilot, Cursor, Gemini, Codex), hands-on practice for varying experience levels
  • Robot navigation UI development
  • Backend: Django (Python), PostgreSQL
  • Frontend: Next.js & React (TypeScript)
  • Docker
2022–2024: Futurepath / CARIAD (Volkswagen Group)
  • Development of a C# .NET 6/8 web application (license management)
  • Backend: EF Core (Code First)
  • Frontend UI: Blazor Server
  • Unit tests & integration tests using xunit, bunit, Moq & FluentAssertions
  • Staging environment & deployment for IIS
  • Micro-Services
  • Excel Imports & Exports using ClosedXml
2018 to 2022: Project for M-Soft (initially via Brunel, direct engagement from 2020)
  • New development of a DMS (Document Management System) with C#, .NET 4.7 & ASP.NET Core 2.2 — updated to .NET 6 over the years
  • Helped shape the architecture from day one (greenfield), including a clean separation of domain core and infrastructure
  • Backend: repositories using EF Core (Code First); full-text search via an integrated Lucene index
  • Frontend: ASP.NET Core, Blazor Server & Razor Pages
  • Testing: unit & integration, ~80% coverage on average
  • Embedded the DMS seamlessly into the existing desktop ERP: via the ERP's built-in browser component plus JS-based communication for automatic single sign-on
  • Security: password hashing, token-based authentication
  • DevOps & Pulumi, version control via TFS and Azure DevOps
  • Sprint planning, paired programming, own coding guidelines
2015–2018 & 2020–2021: Project with Motion Media GmbH
  • Independent architecture planning and new build of a SaaS platform for virtual tours (immo-tours.de).
  • Planned as a multi-service architecture from day one; Java 8/11, Spring Boot, Vaadin.
  • Later added a REST API for the mobile app; CI/CD with JetBrains TeamCity
  • Debugging and troubleshooting
  • Re-engaged by the client after a gap spent on another mandate (M-Soft/Brunel).
2013 to 2015: Project for Gebit Münster
  • C# development of a generalized catalog system; migration of the UI from Silverlight to HTML5 / CSS.
  • Production CQRS/event-sourcing system with a custom event store developed in-house by the team (RabbitMQ as message broker) and domain-driven design.
  • Onboarded via pair programming; after the originating colleague left, took sole ownership and continued developing the system
  • DDD, TDD, and Scrum as standing practice

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