16+ years
software engineering
Experience with business critical product and enterprise systems.
Available from September 2026
Freelance Senior Software Engineer
I build and modernise business critical .NET and Java systems.
I support businesses with backend engineering, APIs, integrations and the incremental modernisation of complex software landscapes. I combine hands on engineering with architecture ownership and technical leadership.
.NET & Java · Backend Engineering · APIs & Integration · Modernisation
Stefan Weyer
Engineering · Architecture · Leadership
Experience grounded in delivery
7+ years
technical leadership
As team lead, technical director and CTO.
End to end
responsibility
From engineering and architecture to deployment and operations.
Project experience across e-commerce, tax processes, healthcare and veterinary software. Project references and supporting evidence are available on request.
Typical challenges
When complex systems need dependable evolution.
I step in where domain complexity, technical debt and delivery pressure converge.
Backend Engineering
Robust APIs, business logic and data models for business critical applications.
Modernisation & Stabilisation
Incremental improvement of existing applications without a high risk wholesale replacement.
APIs & Systems Integration
Reliable integration of external platforms, data sources and enterprise systems.
Technical Ownership
Architecture decisions, code reviews and technical leadership with hands on contribution.
Projects
Selected projects
A selection of my previous projects and areas of responsibility. Client names and individual project details are not published for confidentiality reasons.
Digital nutrition consulting platform
- Role
- Lead Full Stack Engineer & Software Architect
A new digital service required an integrated platform for booking, communication, administration and mobile use.
View project profileE-commerce and tax platform
- Role
- Lead Full Stack Engineer & Software Architect
Complex e-commerce and tax processes needed to be represented transparently, securely and extensibly in one web platform.
View project profileCloud-based practice management software
- Role
- Senior Software Engineer, .NET & Blazor
An established practice platform needed regulatory workflows and external integrations without destabilising existing operations.
View project profileApproach
From understanding the landscape to stable operations.
Good architecture emerges through delivery with traceable decisions, clean code, tests and dependable execution.
- 01
Understand
Capture business goals, existing systems and technical risks.
- 02
Decide
Evaluate solution options and define transparent guardrails.
- 03
Deliver
Engineer, integrate, test and ship hands on.
- 04
Stabilise
Secure operations, maintainability, documentation and knowledge transfer.
Career path
Technical leadership built on engineering practice.
My path led from .NET engineering through project and team leadership to CTO. Today I combine that experience with hands on software engineering and architecture ownership as a freelancer.
View career timeline →- 01Java & .NET Software Engineer
- 02Senior Engineer & Project Lead
- 03Team Lead & Technical Director
- 04CTO & Lead Developer
- 05Freelance Senior Software Engineer & Software Architect
Contact
Looking for support with a demanding software project?
I support businesses with backend engineering, modernisation, APIs and systems integration. I take architecture ownership and technical leadership where they are needed for successful delivery.
- Available from September 2026
- Conversations welcome now
- Remote and hybrid
- Mönchengladbach and Düsseldorf