About
Six domains. One specialist.
stuf.rocks is the service brand of Stefan Köllner — based in Hamburg, with over 25 years of software engineering across web, desktop, embedded data acquisition, Linux server operations and AI-assisted tooling. The shop offers concrete, scope-bound engagements; larger custom work happens by direct arrangement.
The work delivered here is not standard agency output — it comes from a specialist who chooses the stack, plans the architecture, writes the code, operates the servers, and takes on long-term maintenance. Full lifecycle. Architecture principles (loose coupling, testability, extensibility) are non-negotiable: the result is software that can still adapt to new requirements many years from now.
Operates the sister brands <span class="text-white">ndtss</span> (NDT Software Solutions, products in use across Europe and the GCC) and <span class="text-brand">DELTA TEST ME</span>, plus a professional Linux cluster in production for over a decade.
Principles
How the work is done.
Modules know each other through interfaces, not concrete classes. Layers are respected — no shortcuts that come back to bite in year two.
Pure functions where possible, side effects isolated, dependency injection over hidden singletons. Tests are how the code stays alive.
New sources, new views, new filters arrive as extensions, not by patching existing code. Open/Closed in practice.
Logs, metrics, restore-tested backups, runbooks. Software that ships is software that runs — and gets observed when it does not.
Methodology
How delivery happens.
Short iterations, early feedback loops, shippable increments instead of big-bang releases. Direction can adjust without throwing away work.
Working prototypes in days, not weeks. Iterative refinement with the customer — assumptions are validated against running software, not slide decks.
Deliberate user journeys, clear information architecture. Focus on polished, learnable interaction rather than feature sprawl.