OpenAI Codex Experts in Berlin

• Self-employed · Berlin, Germany
• Co-founded the company and own the entire technical side: product architecture, backend, frontend, infrastructure and operations.
• Designed and built the Automated Booking System (ABS) as well as the core platform and payment logic.
• Development of AI-powered SaaS products, from architecture through backend and frontend to production operation.
• Technical consulting on product architecture, data protection and permissible automation.
• Building, running and monetising my own API products for AI agents, each available as a REST interface and as an MCP server.
• Full ownership of architecture, infrastructure, billing, legal texts and go-to-market.

• Reviewed contracts and legal documents, identified risks, and translated complex questions into clear recommendations for non-lawyers.
• Managed debt collection and supported in-house legal advice as well as court appointments.

AI Sales Teammate

• Took Halvday from concept to live product in five months, securing three design partners and two paid engagements, including PlanRadar.
• Built and shipped the product end-to-end as a solo founder, spanning product strategy, frontend, backend, agent orchestration, infrastructure, design, compliance and go-to-market.

• Process analysis and target concept: interviews with responsible stakeholders and users, system and handover model, bottleneck analysis and acceptance criteria.
• Clearly defined automation modules, built with AI support using Python/FastAPI, TypeScript/Next.js, SQL/PostgreSQL, Supabase, REST APIs and Webhooks; specification, acceptance criteria and acceptance testing handled by me.
• Document and decision workflows from intake, research and extraction through to decision documents, CRM updates or controlled system actions.
• Quality assurance and handover with test cases, logging, exception paths, operational documentation and knowledge transfer.

• Own full-stack development of an AI-native enterprise platform built on TypeScript, React, Vite, tRPC, Hono, and PostgreSQL, delivering AI-powered consulting workflows to B2B clients.
• Designed and shipped a multi-agent AI system using ReAct framework and Claude skills-style workflow patterns, including an intelligent PM assistant with rich system prompts, slash commands, tool integrations, and streaming chat UI.
• Architected an LLM evaluation framework: rubric-based LLM-as-judge, golden datasets, regression testing, and automated quality gating — ensuring consistent AI output quality at scale.
• Integrated LangFuse for end-to-end LLM tracing, conversation replays, and evaluation pipelines, enabling data-driven prompt optimisation that reduced token costs and response variance.
• Built with Drizzle ORM, pgvector, and knowledge graphs for structured data access, semantic search, and relationship-aware AI reasoning across the platform.
• Led TanStack React Query migration across the application — replacing manual state management with centralised caching and automatic refetching, reducing data-fetching boilerplate significantly.
• Practiced AI-native development throughout: Claude Code, Codex, Perplexity SDK, and LLM-assisted testing across the full development lifecycle. Deployed on Vercel + Azure ACA with Biome for linting/formatting.

• Built a JTBD-based prioritization framework for 3,000+ accumulated feature requests, identified 27 broker jobs, validated 8 through 25 user interviews, and used the resulting job map as a live prioritization filter for all incoming channels (Upvoty, CSAT, consulting tickets).
• Responsible for the Scout24 Lighthouse initiative: Document Intelligence with full RAG architecture (semantic chunking, bge-m3 embeddings, pgvector, BM25+Dense hybrid retrieval).
• Reduced lead time of customer feature requests to 3.1 days through code analysis, ticket specification, and independent implementation using a coding agent (Codex).
• Developed an LLM-based support agent (GPT-4o mini, Codex-generated merge requests) that reduced 3rd-level escalations from 40% to 5% of all monthly tickets.
• Integrated six partners through technical coordination, specification, backlog and release management, and led seven full stack developers.
• Eliminated regulatory exposure for brokers in six weeks through risk analysis (BGH ruling on distance selling/GDPR), new audit features, and coordination with legal and data protection officers.

• Built core parts of formae's infrastructure engine and cloud integrations in Go, managing resource lifecycles across cloud and Kubernetes environments.
• Designed and implemented an extensible plugin architecture and SDK for integrating infrastructure providers and resources, including AWS, Kubernetes and Helm.
• Built agent-native infrastructure workflows exposing formae through MCP to tools including Claude Code, Codex and Cursor.
• Worked directly with prospective customers on technical evaluations, implementation design and migration paths from existing infrastructure workflows to formae.
• Helped evolve formae through its open-source, multi-cloud and cloud platform releases, with a focus on reliable infrastructure orchestration and developer experience.