Stefan Koshiw

Profile

I work as a CTO, usually in companies where the systems are messy, the constraints are real, and the outcomes matter. Alongside that, I advise early-stage teams, helping them make early technical decisions that leaves a path to growth. Currently I am working full time as the CTO of Fraud0 GmbH.

Over the years I’ve moved between real-time raytracers in CAD, to FinTech and now AdTech — not by design, but because I tend to gravitate toward difficult problems involving scale, latency, and imperfect data.

My day-to-day work is a mix of hands-on coding, system design, and supporting teams as they make technical decisions under pressure. That often means building and operating large data platforms, and increasingly working with applied AI in production contexts.

Recently, I’ve been exploring and building with generative AI — experimenting with agent-style architectures, voice-based interfaces, RAG systems, and semantic knowledge graphs. I’m interested in how these pieces can be composed into systems that are genuinely useful.

When I’m not working, I read a lot, cook often, and spend time bouldering. I live in Berlin with my wife.