Software developer in Berlin. Backend services and the interfaces around them — currently a lot of LLM-backed document processing, plus keeping a grown Java application alive and moving.
Document extraction with language models. FastAPI and Pydantic services that turn scanned administrative documents into structured data. I built the evaluation harness for it: automated comparison of prompt variants against ground truth captured by hand, scored as hit rate rather than equality. A pipeline you cannot measure is a pipeline you cannot change.
Agent platform. Several single-purpose agents behind one gateway, LangChain and FAISS for retrieval, used daily by around a hundred people.
Registry data standards. XMeld over OSCI, part of the German XÖV family. A new protocol version lands every six months and I run that migration. There is no counterpart to ask whether you got it right, so correctness has to come from the specification.
Legacy, honestly. Java 17 with JSF and PrimeFaces. Kept alive and modernised in place instead of rewritten.
DMX lighting control for a Berlin club, written in vvvv, a visual dataflow language. Software, cabling and fixture layout are mine. Running every weekend since 2023 without anyone else maintaining it. Hard real time: roughly 20 ms per frame, and DMX is unidirectional, so you send without acknowledgement and find faults by halving the chain.
Home automation platform. Home Assistant with around 1,100 entities and 120 automations, with a self-built assistant layer on top. The automation layer decides when something is relevant — triggers, thresholds, cooldowns, deduplication. The assistant decides only how it is phrased and through which channel. The language model is deliberately not in the control path: latency, cost, and faults you cannot reproduce.
Final apprenticeship project. A company-wide quiz platform. OpenAPI specification first, TypeScript client generated from it rather than hand-written, Spring Boot and PostgreSQL behind. Built alone and defended before the chamber of commerce examination board.
Contract first. I write the interface before the implementation — OpenAPI in one project, Pydantic schemas in another, a custom event schema in a third. Three projects, same approach, arrived at independently each time. A broken contract should fail at compile time, not at the user.
State over events. An event is gone once nobody picks it up. A fact stays until it has been delivered. Most "the notification never arrived" bugs are this one mistake.
Test what is testable, monitor what is not — and know which class of fault each one catches. Monitoring finds that something is not running. Tests find that something is running wrong.
Python · FastAPI · Pydantic · Java 17 · Spring Boot · TypeScript · React · Next.js · PostgreSQL · Docker · Kubernetes · GitLab CI · LangChain · MCP · vvvv
Most of what I write lives in a private company repository and stays there. What is public here is older or personal. I am slowly extracting the parts of my own setup that make sense standing on their own.