I work with founders and domain experts who know exactly what should exist and need someone to build it. It starts with an honest assessment: what it costs, what gets difficult, and what you are better off not building at all.
Julien Leske
Freelance full-stack developer & consultant for digital product development
Hamburg · regularly in Berlin
Digital products recently delivered
The right tool for your goal
Two days of design thinking, a clear path to numbers you can rely on, and a clickable prototype: the ideal hand-off to your developers, or to Claude Code ;)
How it works →Two days together, exploring ideas, testing feasibility and working the idea into a clear vision. You get a clickable prototype, a technical feasibility assessment, an architecture sketch, a phased roadmap and a cost estimate that holds up. If you want it, I will add a detailed prompt sheet in case you would rather attempt the build with an LLM. All of it is yours, whether or not we build together. Credited in full if you commission the build.
Full delivery, focused on digital platforms, or on programmes and processes with high complexity.
How it works →Full delivery. Web applications, marketplaces, platforms, automated processes. Next.js, TypeScript, Python, Postgres, AWS or Vercel, Shopify, Stripe, and WordPress with WooCommerce if it has to be. I lead every project personally and bring in specialists from my own network: designers, developers with domain expertise, marketing people, when your project needs them. You always know who is working on your vision.
Business, advisory or code sparring. Monthly, cancellable.
How it works →Fortnightly sessions, code review, business consulting, access to my network, architecture decisions, or a second opinion on the roadmap. Monthly and cancellable. Reduced day rates for pre-seed and self-funded founders. Just ask.
Websites and small applications built by hand, not assembled from a template.
How it works →Portfolio sites, brand platforms, booking flows and small applications, built to the same standard as the larger work but at a scope that fits a smaller budget. A CMS you run yourself, real performance, and no page builder to fight later.
6 typical steps for a successful collaboration
Map stakeholders, competitors and constraints
What ecosystem does the project sit in? What do the stakeholders actually need? Who else is in the market? We settle all of that at the start, in a kick-off workshop.
Weigh up technology, architecture and strategy
We look at where the project stands and assess the existing technology, architecture and strategy, so we can agree the KPIs early and use what you already have.
A working demo every two weeks
There is a running demo every two weeks. Alongside the development itself, the aim is to test with users, stakeholders and regulators on that same rhythm and collect feedback. The cadence can be set to whatever the project needs.
From MVP to finished product
Where the project allows it, I would rather launch early and extend continuously against feedback and new requirements. On greenfield projects that is what produces early results, and early revenue.
Including after hypercare
With every major release at minimum, we evaluate the results, draw conclusions and adjust the strategy where it needs adjusting. I like to use GDPR-compliant analytics alongside qualitative feedback rounds with stakeholders and users.
From go-to-market to expansion
Once the product has proved itself, I support vertical and lateral expansion into new markets, and the scaling of both infrastructure and new features, so growth can continue.
In detail
Currently in progress
Lexikal
Own product
A German reader that rewrites real news to six CEFR levels. The hard part was never the reader. It was making “simplified” mean something a teacher would accept.
Burnout Help Berlin
Product Development
A burnout self-check built on a clinically validated instrument: anonymous, no account, no tracking, and no email capture, on purpose.
More projects
In their words
Not just code quality, but the ability to take a domain expert’s vision out of their head and turn it into something that works, at a fair price.
What impressed us most was his ability to understand our scientific and educational vision and turn it into a functional and elegant digital platform. Julien's strength is the rare combination of creativity, technical competence, and the ability to listen deeply, understand ideas, and transform them into reality.
Prof. Dr. Jeanette Schulz-Menger
Circle Institute
Beyond his abilities as a developer, we particularly value his project management, which helps us deliver what we set out to do efficiently and on target. Working with him is of great value to us.
Lars Hahne
Founder & CEO
Julien is an extremely innovative and customer-focused product developer. I particularly appreciate his exceptional consulting skills and his ability to implement solutions quickly. I find the combination of a wide range of options and a tailored selection to be very valuable.
Anna Kauert
Trainer & International Communications Coach
Start here
