Freelancer profile translated to English.
Back to original languageAbout Rainer
Frontend & AI Agent Engineer with a focus on scalable product architectures. I develop iOS and Android apps with React Native/Expo, web products with React/Vite, and production-ready, reliable AI agent workflows with Agent Development Kit (ADK).
Since 2004, I have successfully launched over 50 mobile and web projects – from WordPress, Shopify, Ionic, and AngularJS, to specializing in the React and React Native ecosystem since 2019, and today developing architectures for intelligent, autonomous agent workflows.
Programming Languages: Strong Experience: TypeScript & JavaScript (via Node.js, React, and React Native). Medium Experience: Python (via AI agent development), Angular 2+/AngularJS (via Ionic Apps), Objective-C/Swift or Kotlin/Java (Native via React Native & Ionic, Capacitor, Cordova), Dart (via Flutter Apps), PHP (via WordPress).
Mobile (Cross-Platform), Web & Frameworks & Tooling: React Native, Expo, React.js, Next.js, React Native Web (RNW), React Navigation, Tamagui, NativeWind, Vite, One, Gatsby, TanStack, Redux, Turborepo (Monorepo), CI/CD (EAS, GitLab/GitHub CI), Docker, IAP (In-App Purchases), OTA Updates, Deep Linking, App Signing, Push Notifications (FCM, OneSignal), Dynamic SEO/Microdata, SSR/SSG.
AI Agent Development with Python (uv-first): Google Agent Development Kit (ADK), Vertex AI, RAG, Tools, Agent Permissions, Generative UI Primitives, AG-UI, SSoT, HITL Gateways, Evaluation, Observability, MCP.
Quality & Testing: Jest/Vitest (Unit Testing), Biome (Linter/Formatter), Playwright (E2E), Sentry, Husky, Crashlytics, Code Reviews (GitLab MRs), ruff, and mypy.
DB/Backend/API/Cloud: GraphQL, REST APIs, Google Cloud Platform (GCP, Cloud Run, Cloud Build, IAM, Cloud Storage, Secret Manager), PostgreSQL (via Cloud SQL), SQLAlchemy (ORM), NoSQL with Firebase and MySQL (WordPress).
Project Management (Agile): Scrum/Kanban with Atlassian (Jira, Confluence), Notion & Linear.
German
Native or bilingual
English
Fluent
Remote only
Primarily works remotely
Experience
- appamass - AI Agents & App Development StudioFrontend & AI Agent Engineer (AI, App & Web)DIGITAL AND ITApril 2004 - Today (22 years and 4 months)Las Vegas, United States- Mobile app development with React Native/Expo (TypeScript)- Web development with React & Vite (TypeScript)- AI agent development with Google Agent Development Kit (ADK) (Python - uv-first)Present: An AI agent with 21 specialized sub-agents for creating, curating, validating, and orchestrating blog posts, and a social media marketing agent with two sequential orchestrators and four sub-agents. Both run productively on Cloud Run with a scheduler job. [TechStack: ADK, Python uv-first, GCP, IAM, Cloud SQL (PostgreSQL), SQLAlchemy, Gemini]Nov. 25 – Feb. 26: Part of a 6-person enterprise developer team of an IT service group for the complete refactoring of the iOS and Android apps of an Austrian public law institution (400k users). [Tech-Stack: React Native/Expo, custom styling kit, Redux Toolkit, REST API, Axios, Storybook, Biometric Auth]Nov. 25 – Feb. 26: Upgrade of a long-standing iOS & Android app at an IT service company (100k users). [Tech-Stack: iOS, Android, Vite, Capacitor]Before: Four React Native/Expo apps and three Ionic apps with Capacitor/Cordova. 18 websites with various React frameworks (Gatsby, Next.js, Remix, One), Tailwind, Tamagui, or custom style kits – as well as React Native Web (RNW), Mithril.js, PWAs with AngularJS, and CMS projects with WordPress, Wix, and Shopify.
- IT service agencySenior Web & App DeveloperDIGITAL AND ITJuly 2024 - July 2025 (1 year)Wien, Austria- Mobile app development with React Native/Expo (TypeScript)- Web development with React (TypeScript)Lead on a Health & Fitness app, iOS & Android, Greenfield. [Tech-Stack: React Native/Expo, Auth & CRM, IAP Subscriptions, Push Notifications]Lead on a two-wheeler security app, iOS & Android, Greenfield. [Tech-Stack: React Native/ Expo, custom stylesheet kit, Stripe API, QR Scanner, UX/UI Lifecycle Tools]Lead of an existing event/festival app during refactoring, iOS & Android (+10k users). [Stack: React Native/Expo, Debugging, Offline-first/Caching via TanStack Query]Developer (in team) of a Gastro Bonus app, iOS & Android, Greenfield – as well as lead for the architecture of a monorepo. [Stack: React Native/Expo, REST API with State & TanStack Query, Turborepo, MUI, Supabase]Developer (in team) for the optimization of an existing smart home control app, iOS & Android. [Stack: ~300k users, React Native, Electron, preparation for NewArch, Data Handling]Developer (in team) on a smart home B2C/B2B2C web shop and lead for dynamic SEO & Microdata setup. [Stack: Next.js, Turborepo, GraphQL, custom CI/UI kit, i18n for 13 languages]
- Digital media agencyMid & Srn App & Web DeveloperDIGITAL AND ITAugust 2020 - February 2024 (3 years and 6 months)Wien, Austria- Mobile app development with React Native/Expo, Flutter, Ionic (JavaScript, Angular/AngularJS, Dart, Swift, and Kotlin/Java)- Web developmentIn total, six React Native apps, seven Ionic apps with Capacitor or Cordova, as well as two Flutter and two native iOS and Android apps – all maintenance or greenfield projects.Additionally, I was responsible for the App Store and Google Play presence of all agency apps (total approx. 600k MAUs), including release builds/rollouts and ASO.Web Development: Independently or as part of a team for a total of nine WordPress projects (Divi, Elementor, or WPBakery) and five larger Shopify shops.
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Education
- Master Craftsman / Qualification ExaminationAustrian Economic Chambers1998