1&1 | Germany | 63xxx, 56xxx, 76xxx, 40xxx Karlsruhe, Frankfurt, Krefeld, Montabaur | Permanent position | Full time / Home office | Published since: 28.05.2026 on stepstone.de
Prompt Engineer (m/f/d)
1&1 is one of the leading telecommunications providers in Germany with over 3,100 employees and nearly 16 million customer contracts. With pioneering spirit, unusual ideas and creative teams, we have won a leading market position in mobile and broadband connections. By combining the over 67,000 km long 1&1 fiber optic network and regional networks, we create Germany's most extensive fiber optic network. We also build the most modern 5G network in Europe, based on the new Open-RAN technology. With open interfaces and 5G functions in a powerful cloud infrastructure. Continue the 1&1 success story by designing the future through the deployment and development of innovative technologies. Be part of 1&1. .
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Your tasks • Your profile • What we offer
In this role, you develop powerful prompt and conversation architectures for productive GenAI applications and significantly shape the quality standards in handling LLMs. Building and further development of a central prompt library including versioning and review processes Design and optimization of multi-turn conversations as well as complex agent flows Development of evaluation frameworks (e.g. Golden Sets, Regression Tests, A/B Tests) to ensure consistent quality Monitoring and optimization of grounding quality, hallucination risks and relevant performance KPIs Definition and Establishment of Standards for Structured Outputs, Tool Calling and Safe LLM Interactions Close cooperation with AI/ML Engineering, product teams and customer operations Continuous improvement of prompt strategies for business impact and user experience
Successfully completed studies, e.g. in Computer Science, Linguistics, Data Science or a comparable degree programme Multiannual experience in Conversational AI, LLM engineering or comparable fields Practical experience with productive LLM systems and APIs Knowledge of Prompt Design, Structured Outputs and Tool Calling Good Python skills for integration and automation of workflows Understanding central LLM risks (e.g. Prompt Injection, Hallucinations) Experience with multilingual conversation systems Knowledge of RAG architectures and agent orchestration Experience in the integration of Prompt workflows in CI/CD processes
- Attractive salary
- Strong community of team players
- Working hours of confidence with flexible classification and the possibility of working up to 40% mobile
- Numerous training options on- and offline
- Discounts on 1&1 products and for various leisure activities
- In-house restaurant
- Free drinks and fresh fruit
- Jobrad grant
Location
 | 1&1 | |
| 76137 Karlsruhe, Frankfurt, Krefeld, Montabaur | ||
| Germany |
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