06.10.2026 aktualisiert

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100 % verfügbar

Senior Full-Stack & AI Engineer | React, Node, Python, RAG, LLMs | Red Teaming | ex Microsoft & eBay

Berlin, Deutschland
Weltweit
Berlin, Deutschland
Weltweit

Profilanlagen

CV Radoslaw Fabisiak 2026.pdf

Über mich

Senior Software & AI Engineer with 14+ years of experience, including Microsoft and eBay. I build scalable React/Node.js applications and production AI systems (LLMs, RAG, AI agents) using Python/FastAPI. I also specialize in AI security and red teaming. Available for B2B contracts.

Skills

AI AgentsRAGGitHub CopilotTailwind CSSLLMOpenAICopilotLangChainWeb InterfacesHTMLJavaScriptAmazon Web ServicesHTML5AutomatisierungMicrosoft AzureCSSMobile Application DevelopmentWeb-Content-Management-SystemePythonPostgreSQLNode.jsSoftware ArchitectureRedisAngular 2+Red Team (Netzsicherheit)Reverse EngineeringSQLTypeScriptWorkflowsGoogle CloudTailwindReact.jsPrompt EngineeringVue.jsGoogle FirebaseBackendFastAPIKubernetesPlaywrightFull Stack EntwicklungCloudflareTeam ManagementGraphQLReact NativeCeleryFront EndApi DesignNestJSArtificial Intelligence Markup Language (AIML)Docker
I'm Radek Fabisiak, a Senior Full-Stack Software Engineer and AI Engineer with 14+ years of commercial experience, including enterprise projects for Microsoft and eBay.

I specialize in building scalable software applications, designing backend systems, integrating AI technologies, and solving complex engineering challenges. I'm equally comfortable working hands-on as a developer or taking technical ownership of projects and engineering teams.

Core Expertise

Full-Stack Development
  • JavaScript, TypeScript, React.js, Node.js, React Native
  • Angular, Vue.js, Next-generation web applications
  • REST APIs, GraphQL, PostgreSQL, MongoDB, Redis
  • AWS, Docker, CI/CD, testing and performance optimization
Backend & Software Architecture
  • Node.js, NestJS, Python, FastAPI
  • API design, system integrations and scalable backend development
  • Database architecture, caching and performance optimization
  • Refactoring, modernization of legacy applications and technical migrations
AI Engineering & LLM Development
  • Python, LangChain, LangGraph, OpenAI APIs
  • AI agents, RAG systems, LLM applications
  • Vector databases, embeddings and semantic search
  • AI workflow automation and production AI integrations
AI Security & Red Teaming
  • Prompt injection and jailbreak testing
  • LLM security assessments and data leakage testing
  • AI vulnerability analysis and adversarial testing
  • AI risk assessments and EU AI Act technical considerations
Technical Leadership
  • Leading and mentoring engineering teams
  • Architecture design and technical decision-making
  • Code reviews, testing strategies and engineering quality
  • Working directly with stakeholders, clients and product owners
Selected Achievements
  • Microsoft: Led the migration of a large-scale ASP.NET platform serving 20M+ monthly visitors to React.js.
  • eBay: Developed React and TypeScript solutions and improved application responsiveness by 20%.
  • Performance Optimization: Reduced server load by 70% through caching and API optimization.
  • API Efficiency: Eliminated 500,000 unnecessary API calls per month in a mobile application.
  • Engineering Leadership: Led a team of 10 developers and delivered complex applications under tight deadlines.
  • AI Engineering: Developed AI-powered automation systems and applications using Python, FastAPI, LangChain and LLM APIs.
What I Can Help You Build
I can join an existing development team, take ownership of a technically challenging project, modernize an application, design a new system or integrate production-ready AI features into existing software.

My approach is pragmatic: clean architecture, maintainable code, reliable delivery and measurable results.

Available for freelance / B2B contracts in Senior Software Engineering, Full-Stack Development, Backend Development, AI Engineering and Technical Leadership.

Erfahrung

Berufserfahrungmehr als 10 Jahre
Freelancer seit2009

Sprachen

DeutschgutEnglischverhandlungssicherPolnischverhandlungssicherTschechischverhandlungssicher

Projekthistorie

AI Engineer & Full Stack Developer

Noble Lynx

Python & AI Agents Developer | Invra

Invra

Internet und Informationstechnologie

10-50 Mitarbeiter

  • Developed and deployed AI solutions using Python, FastAPI, Playwright, LangChain, Celery, Redis, and OpenAI APIs.
  • Built core functionality for two major projects: an AI Sales Outreach Agent and an AI Language Tutor, implementing automation, natural language processing, and scalable task orchestration.

Lead Developer | Duomly

Duomly

Internet und Informationstechnologie

10-50 Mitarbeiter

  • Designed and implemented backend features for E-learning and Marketplace apps using Node.js, TypeScript, and AWS Serverless.
  • Developed front-end & mobile interfaces using React.js and React Native, enhancing UX for 10,000+ users monthly.
  • Led technical strategies and mentored a team of 10 developers.

Senior software engineer | eBay

Ebay / mobile.de

Automobil und Fahrzeugbau

>10.000 Mitarbeiter

Ebay / mobile.de

Project:
Online Automotive Industry Project:
Frontend: React.JS + Typescript + HTML5 + CSS3

Responsibilities:
* Planning, designing and creating experimental
prototypes of the frontend and data providing
layers
* Development of new features in front-end and
back-end
* Working on performance and tech stack
improvements

Senior software developer | Microsoft

Microsoft

Internet und Informationstechnologie

>10.000 Mitarbeiter

Microsoft

Project:
Online communicator:
Frontend: React.JS + Javascript + HTML5 + CSS3

Responsibilities:
* Planning, designing and creating experimental
prototypes of the frontend and data providing
layers
* Planning, designing, implementing and techmentoring
process of huge frontend codebase
migration from ASP.NET + Javascript to React.js
* Planning, designing and implementing process of
create data providing layer
* Development of new features in front-end

Lead developer

UC
UC

Project:
Marketplace:
Frontend: React.JS, Javascript, GraphQL, Redux
Backend: Node.JS, Nest.JS, PostgreSQL,
Typescript, AWS
Mobile: React-Native

Responsibilities:
* Help company to lead developers, resetup and
finish delayed project (finished with success)
* Designing project backend architecture with
nestjs and node.js
* Designing and implementing security for backend
in node.js, nestjs and GraphQL API
* Designing project relational database
* Develop features for frontend
* Developer features for backend
* Develop features for mobile platform

Senior full-stack javascript developer

24i media
24i media

Project:
Sport App:
SmartTV app: Javascript ES3
Frontend: React.JS, Javascript, HTML5, CSS3

Responsibilities:
* Creating app for web and smart TVs
* Manually testing apps and adjusting for different
tv devices
* Developing frontend features for web app

Senior full-stack javascript developer

Cemex / Neoris

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