I'm Björn Mergemann — CTO on demand, engineering leader, and someone who still writes code every day. For 15 years I've taken products the whole way: from a rough idea on a whiteboard to software running in production that people depend on — and that earns its keep for the business, not just the codebase.
Most products don't fail on technology. They fail in the gaps — between strategy and execution, design and code, the demo and production.
That's the space I work in. I've been the senior developer untangling a legacy codebase, the engineering lead hiring and shaping a team, and the CPTO in the strategy meeting — often in the same week. Because I've actually done each of those jobs, I move between them without anything getting lost in translation.
My approach is pragmatic and direct. I find the real problem — not the feature request, the problem underneath it — and build the simplest thing that solves it: robust enough to scale, simple enough to stay fast. And I name the hard things early. The decision everyone is circling, the elephant in the room — surfacing it beats letting it quietly sink the project.
Most of all, I build for the long run, people included. Whether I'm embedded in your team for a few months or steering as your CTO on demand, I leave things stronger than I found them: cleaner architecture, sharper priorities, and engineers who own their work and want to keep shipping. I care about the team as much as the product.
When you need senior technical leadership but not a full-time CTO, I step in: owning architecture and roadmap, and making the hard calls — what to build, what to buy, what to kill before it burns a quarter. I weigh engineering cost against business reality, then decide. And I am the honest bridge between what the business dreams up and what the team can realistically ship — uncomfortable truths included.
Engineering is only half the job. I help shape the product itself — the concept, the priorities, the UX — so the team builds the thing that matters instead of dutifully shipping the wrong spec. I push back on features that will not pay off, and the right questions early save quarters of rework later.
I have built engineering teams from a single hire and grown developers into leads. I set up the high-trust culture, rituals and standards that let a team own its work and enjoy shipping together — then make sure it all outlasts me.
I take products from first prototype to production-grade system. With AI I can stand up a working prototype in next to no time — and fifteen years of experience is what turns it into something production-ready in days, not weeks. Frontend, backend, database, infrastructure: one person carries it through, so nothing leaks away in handoffs.
I build AI that holds up outside the demo: agents that complete real tasks, RAG pipelines grounded in your own data, and LLM features wired into the workflows people actually use. I also know when AI is the wrong tool — and I will tell you.
I design, deploy and operate infrastructure on AWS and Google Cloud, or self-hosted on your own servers when cost, data control or sovereignty demand it. Same rigour either way — automated, observable, and something you can sleep soundly on.
I'm a TypeScript specialist at heart, but I choose tools to fit the problem, not the other way around. Here's what I reach for most — and what I've shipped to production again and again.
The non-code work that decides whether software actually succeeds.
TypeScript end to end — the same language and types from database to UI.
Whatever the project needs, built fast and accessible.
APIs and services that stay maintainable as they grow.
Shipped and operated, not just provisioned and forgotten.
Production AI, not demo-day theatre.
Deeper into the product, and closer to the people building it. From senior developer to CPTO — every step hands-on.