Senior AI Engineer – TypeScript / LLM Systems (DRWN)

Job title – Senior AI Engineer (TypeScript / LLM Systems)

Client Location – Cologne, Germany

Remote work offering – Hybrid, 2 office days per week

Client Industry – AI / Software Technology

Contract Length – Ongoing freelance engagement (length to be confirmed at interview)

Contract type – Freelance

Project focus

You’ll take ownership of live, production LLM systems: content generation pipelines, retrieval-augmented generation (RAG) over internal documents, and automated workflows tightly integrated with core business systems. The stack is TypeScript and Next.js end to end, and this is applied engineering on systems already in production, not model training or fine-tuning.

Key skills and Experience required

• Professional experience owning at least one LLM-based system in production, including incident handling
• Advanced TypeScript and Node.js: strict typing of non-deterministic model output, async/concurrency patterns, streaming responses, structured error handling
• Next.js in production: App Router, route handlers, server actions, streaming to the client
• Proven track record taking over and improving existing codebases under live production traffic
• Practical retrieval expertise: hybrid search, embedding model selection, cross-encoder reranking, metadata filtering, permission-aware retrieval, and structured diagnosis of poor retrieval quality
• Experience processing real-world documents (PDFs with tables, scanned material, DOCX, HTML), including layout-aware parsing, OCR, and evidence-based chunking
• Structured outputs and tool calling as everyday practice: JSON Schema, Zod or comparable runtime validation, function calling, handling malformed/partial output, context window management
• Experience designing and running LLM evaluations, plus tracing/eval tooling in a TypeScript codebase (e.g. Braintrust, Langfuse, Promptfoo, OpenTelemetry/Arize Phoenix)
• Familiarity with Postgres and vector search (pgvector or comparable), Docker, Git, CI/CD, and a major cloud platform
• Hands-on experience with the Anthropic and/or OpenAI TypeScript SDKs
• Confident English communication; German is a plus

If this role is of interest, please apply with an updated CV.

Darwin Recruitment is acting as an Employment Business in relation to this vacancy.

Marvin Mills