twentyfirst.dev — Product engineering
We build apps, websites & everything between.
From MVP to production scale — a senior team that designs, codes, and ships modern web and mobile products. AI-first, EU-based.
Design. Build. Ship.
Web applications
Dashboards, SaaS, and internal tools built on Next.js & React — fast, accessible, maintainable.
Mobile apps
Cross-platform iOS & Android from one codebase, with native-feeling UX.
Websites & marketing
High-performance marketing sites with CMS, SEO, and i18n out of the box.
AI integration
LLM features, RAG, agents, and automations wired into your product safely.
Cloud & DevOps
CI/CD, infrastructure-as-code, observability, and managed deployments.
MVP & prototyping
From idea to a working, fundable product in weeks — not quarters.
Products we've shipped.
FlightPilot24
EU flight compensation platform helping passengers claim refunds under EU261.
Twentyfirst.ai
Unified AI model marketplace — thousands of models, no-code access, GDPR-aligned.
TravelPilot24
German travel deal publication covering flights, business class, miles, and hotels.
A tight, transparent loop.
Discover
Goals, scope, and a clear plan.
Design
Flows, UI, and a clickable prototype.
Build
Iterative sprints, demoed weekly.
Ship
Launch, monitor, and iterate.
Modern, boring-on-purpose tools.
We pick proven, well-supported technology so your product is fast to build and easy to maintain.
Have something to build?
Tell us what you're building. We'll come back with a plan, a timeline, and a fixed first milestone.