App development for DACH companies that want to grow fast — speed and stability, without the tech debt.
Four projects, told briefly: from problem to measurable outcome. The throughline — ship faster without the architecture paying for it.
01 · MediaMarktSaturn · Mobile architecture
02 · ON AG · AI · E-commerce
03 · Purelei · E-commerce
04 · BRACK.CH · E-commerce · Retail
A clear, repeatable process makes speed predictable and architecture resilient. Modern tooling compresses the routine work — the judgement stays human.
Sharpen goal, scope and success criteria together. A clear spec, not a vague wishlist.
Modular architecture from day one. AI-assisted routines speed things up; reviews keep quality high.
Automated tests, performance and crash monitoring. Evidence over gut feel.
CI/CD all the way to the stores. Clean handover, documented and maintainable.
Flutter and Dart at the core, plus a toolchain that automates the repeatable. Not "AI builds your app" — just less friction per release.
Flutter
Dart
Riverpod
Firebase Freezed
Fastlane
Sentry
SvelteKit
React
Tailwind CSS
Vite
NestJS
FastAPI
Prisma
PostgreSQL
Redis
Strapi
Docker
GitHub Actions
Playwright
Claude Code
OpenSpecWonderful, professional collaboration! K. laid the foundation for our entire mobile app development. Highly recommended!!
Andre Gröschel TrippleACode GmbHProfessional, results-oriented, always friendly collaboration. To be recommended without reservation. Thank you, K.!
Timo Mugele Framegrabber GmbHK. won us over with clear communication and full commitment. We can only recommend working with him.
Tim Schröder MassiveMiniTeam GmbHKhalid has both, self-organization and autodidactic knowledge and abilities, thus he is stepping out, compared to regular flutter developers!
Max Arbeiter SnapNext GmbHK. was a very valued colleague in my department. He was very reliable and always happy to support others in the team.
Andreas Partenhauser MediaMarktSaturn Technology GmbHWonderful, professional collaboration! K. laid the foundation for our entire mobile app development. Highly recommended!!
Andre Gröschel TrippleACode GmbHProfessional, results-oriented, always friendly collaboration. To be recommended without reservation. Thank you, K.!
Timo Mugele Framegrabber GmbHK. won us over with clear communication and full commitment. We can only recommend working with him.
Tim Schröder MassiveMiniTeam GmbHKhalid has both, self-organization and autodidactic knowledge and abilities, thus he is stepping out, compared to regular flutter developers!
Max Arbeiter SnapNext GmbHK. was a very valued colleague in my department. He was very reliable and always happy to support others in the team.
Andreas Partenhauser MediaMarktSaturn Technology GmbHFrom a no-strings intro call to a long-term partnership — clearly scoped, so both sides quickly know if it fits.
We clarify your idea, feasibility and a realistic timeframe.
Focused help on performance, crashes, migration or an MVP in weeks.
A reliable mobile partner for roadmap, maintenance and continuous releases.
Sending external_id created duplicate Klaviyo profiles next to the Shopify sync. Unsubscribe needs a Klaviyo flow with webhook, not an API call.
12 min · Read more →
Klaviyo pushes silently dropped, taps swallowed by firebase_messaging, Android channels stuck at wrong importance. Three bugs, code fixes included.
12 min · Read more →
One tracking call reaches Firebase, Klaviyo, and Google Ads via an AnalyticsDispatcher with per-provider adapters, consent gating, and error isolation.
12 min · Read more →
I'm a freelance app developer in Berlin and I've been building apps for over seven years — most of that with Flutter.
My focus is a rare combination: ship fast while leaving behind architecture that scales with you. The exact spot where speed usually creates tech debt is where I like to work most.
Depending on scope, a few weeks rather than months. In the intro call we define scope and timeline realistically — honest beats over-promised.
It depends on scope. A lean MVP costs significantly less than a fully-featured platform. Instead of a flat quote, you get a concrete, project-specific estimate in the free intro call — whether you need a new app built from scratch or want to improve an existing product.
Yes. Performance issues, high crash rates, migration to Flutter or stabilising a grown app are among the most common requests. Whether building an app from scratch or improving an existing one — both are everyday work.
An MVP with core features typically takes 6–12 weeks. A more complex app — integrations, backend, multiple platforms — more like 3–6 months. Either way, we create a realistic timeline at the start that matches the scope.
Cleanly documented, tested and maintainable. The goal is that your team can keep building independently afterwards — no lock-in to me.
If app development isn't your core business, building it yourself is rarely cost-effective. An experienced developer ships faster, avoids common pitfalls, and delivers a codebase your team can maintain independently. In the intro call, we discuss whether an MVP makes sense as a starting point — saving budget while testing the idea early.
A 30-minute intro call is free and no-obligation — and you'll know afterwards if it's a fit.