Consumer fintech, zero to 100k users
Mobile and backend lead from an empty repo to 100k MAU. Auth, KYC, payments and trading core, shipped to production in nine weeks.
Fullstack software engineer Maciej Jaros — building mobile, web and desktop applications for clients across Silesia (Katowice, Gliwice, Zabrze, Chorzów) and globally. Stack: Next.js, React Native, Flutter, TypeScript, AI integration, cybersecurity.
You talk directly to the person building your software. No middlemen, no time lost re-explaining the same vision.
I don't sell time spent at the screen. You invest in a working solution that actually grows your business.
I run the process end to end. Instead of managing yet another vendor, you get a partner who turns your vision into a stable product and guarantees real peace of mind.

Engagement process
We hop on a short call. You sketch out your project or problem, and I tell you straight up whether my skills are the right fit for what you need.
What you get: You save time. After 20 minutes you know whether we're on the same wavelength — without spending a single dollar, with zero risk.
If I see I can help, I come back to you with specifics: a clear cost estimate and a realistic timeframe for the project.
What you get: Full predictability and safety. You know exactly what budget you need and when you'll see the first delivered results. No surprises down the road.
Together we pick the model that best fits your project's dynamics (e.g. fixed-scope quote or ongoing retainer). We sidestep corporate bureaucracy.
What you get: Lightning-fast start and flexibility. You don't burn weeks on lawyer back-and-forth, and your budget stays protected.
You get the full picture and the ball's in your court. If you decide to work together — I sit down to code right away. If not — we shake hands and go our separate ways.
What you get: Comfort in deciding. You make the call cool-headed, on hard facts, with zero pressure or pushy sales.
Sound right? Let's start with the first, no-obligation step.
Expertise
Six areas of expertise — from MVP to production-grade products. I focus where I actually ship stable outcomes.
Reliable iOS and Android apps from a single codebase. I use Flutter to deliver smooth, native experiences without doubling the cost of two separate teams. From the first screen, through offline-first architecture, all the way to App Store and Google Play deployment.
Fast, scalable platforms on Next.js and TypeScript. I build web applications that load instantly, rank well in search, and handle heavy business traffic without breaking a sweat. Solid, modern architecture ready to scale with your company.
I bring mobile and web experiences straight onto your customers' computers. Performant, native apps for Windows and macOS (built with Flutter) that integrate cleanly with the operating system. Zero compromises on performance.
I free up your time and your team's. I deploy AI (LLMs, RAG) to automate repetitive, time-consuming processes in your business. Concrete, production-grade solutions that actually cut operating costs — not demos that just look pretty.
Security baked into the code from day one, not glued on at the end. I secure web, mobile and desktop apps to current standards (OWASP). Resilient architecture, safe authentication, and sealed sensitive-data flows.
Your previous developer disappeared and the app is falling apart? I take the wheel. Deep code audit, hunt for critical bugs, patch holes, restore system stability. I get projects back on track so you can sleep at night again.
Work
A few engagements worth talking about. Numbers come from production — not pitch decks.
Mobile and backend lead from an empty repo to 100k MAU. Auth, KYC, payments and trading core, shipped to production in nine weeks.
Rebuilt a legacy Magento stack into custom Next.js + Shopify. Removed friction from checkout, tripled conversion on mobile.
Designed and shipped an internal knowledge platform with embedded AI search. Replaced four legacy tools across 12 teams.
Drivers app + dispatcher console for a regional last-mile carrier. Cut average stop-time variance in half.
Looking for similar results for your product?
FAQ
If your question isn't here, let's cover it on a call. You'll get the answer in writing afterward.
You work directly with the person building your product — not with middlemen. You pay for delivered results, not billed hours, so dragging the work out is against my own interest — I want you to see your idea live as fast as possible. We cut all the administrative overhead and decision-making delays. The total cost of delivery typically ends up clearly lower than hiring and maintaining a multi-person team for many months, and the product reaches the market faster — often in half the time a large agency would need.
You're buying agency and experience in shipping products from zero to market — not just billable hours. You don't pay for vacation, sick days, multi-month team onboarding, or expensive mistakes from inexperienced developers. It gives you a predictable total cost-to-deliver and protects your capital from being burned on bad architectural decisions.
I pick tools for your business goal, not for my own convenience or amusement. Your product is built on industry standards, which protects you from vendor lock-in. The code will be transparent and standardized enough that any other team can take it over later — without rewriting from scratch.
Yes. Before we move to coding, I can prepare several visual mockup proposals (in Figma) and walk you through them in a meeting. That way you know from day one what the product will look like. Once you approve a direction, you have my guarantee that the finished app — whether it ends up running on a phone, a computer, or in a browser — will mirror the approved design pixel-perfect.
I also embed in existing projects as expert support. I take on the hardest technical work and structure the architecture so the rest of the team can move faster. That radically speeds up your time-to-market for new features and bypasses the multi-month, expensive process of hiring an experienced senior in-house.
We sign an NDA and a B2B agreement with a hard IP-transfer clause. Code goes straight onto your servers from day one, so you're its sole owner the entire time. That clean legal posture protects your company's valuation and prevents problems during legal and investment due diligence on a future funding round or sale.
We always start with a short, paid trial period. Within a few days you see in practice whether I deliver what I promised, how I communicate with you and your team, and whether I implement the architecture precisely and consistently follow the testing approach in your project's documentation. That way you make the long-term commitment — and capital decision — based on hard results inside your business, not promises on paper.
That's the target — and best — outcome for your business. I work in a 'build and hand off' model. At the right moment I help you define requirements, technically interview the first hires for your team, and onboard them into the project. You build operational independence and smoothly take control of the technology exactly when keeping in-house developers becomes cost-effective for you.
We work on a monthly retainer, invoiced in advance from a Polish company in your chosen currency (PLN, EUR, or USD). You know upfront what you'll pay at month's end — no hidden costs. For you it makes financial planning easier; for me it locks in focused time to deliver your business without distractions. We realistically start within 7 to 10 days of agreeing on terms.
Contact
Tell me what you're building. I'll come back with thoughts and a first shipping date.