(Junior) Data Scientist (m/f/d) Search / AI Forge

About this job

CHECK24 is the comparison portal: market leader and dynamic start-up in one. In agile teams, we make quick decisions and operate with flat hierarchies. With state-of-the-art tools, technologies, and cutting-edge AI methods, we drive data-driven innovation – always with the goal of creating real added value for our customers. Across more than 50 products, we work daily to further improve the user experience for our more than 20 million customers.

Our Search Team within the CHECK24 AI Forge develops scalable AI solutions for search and ranking across various CHECK24 products. Search is a central entry and navigation point for our customers and covers demanding domains – from e-commerce product search and web-like navigation to travel search for hotels, destinations, and other products.

Search and ranking are among the most demanding disciplines in applied machine learning. A good system must understand user intent, retrieve relevant candidates, rank them effectively, and meet high demands for latency, scalability, and measurable customer value. Many of the questions we work on are technically complex and cannot be answered with standard solutions – they require an analytical, hypothesis-driven approach as well as solid engineering.

To strengthen our team, we are looking for someone with initial practical experience who systematically analyzes complex problems, rigorously evaluates approaches, and wants to develop into a strong Applied Machine Learning Engineer (m/f/d). You will work on production systems that combine classic information retrieval methods, deep learning, embeddings, and large language models, and you will be involved in the entire lifecycle – from the initial idea through evaluation to deployment, monitoring, and continuous improvement. A particular focus will be on agent-based workflows: the design, evaluation, and productive use of systems that autonomously utilize tools and solve multi-stage tasks.

We look forward to receiving your application for the position of (Junior) Data Scientist (m/f/d) Search at CHECK24 AI Forge GmbH.

What you bring

• You have successfully completed a degree (ideally a Master's) in computer science, mathematics, statistics, physics, electrical engineering, or a comparable quantitative subject, with strong grades in quantitative subjects.
• A solid understanding of ML fundamentals and systematic model evaluation allows you to assess model performance in a well-founded manner, test hypotheses, and provide comprehensible justifications for improvements.
• You bring at least one year of relevant practical experience in machine learning or data science, including from student work placements, internships or your own projects.
• Strong Python skills and practical experience with ML or deep learning frameworks like PyTorch are part of your technical toolkit.
• Solid classic ML skills such as gradient boosting, regression, and feature engineering are evident in your resume – beyond LLM or RAG applications.
• You have practical experience with LLM-based applications, LLM evaluation, tool use, or agent-based workflows.
• Practical experience with APIs (e.g., FastAPI), containers, and Git – ideally including a self-deployed service – complements your interest in building complete, production-ready systems.
• Knowledge of information retrieval, semantic search, recommender systems, or learning-to-rank is advantageous.
• Good English skills (at least C1 level) round off your profile; German skills are a plus, but not a requirement.

Your tasks include

• You create robust evaluation datasets and metrics and validate improvements through offline evaluations, user signals, and A/B testing.
• You research promising approaches in Information Retrieval, Recommender Systems and Large Language Models and translate them into measurable customer benefits.
• In model development, you rely on training, fine-tuning, and systematic evaluation – with a focus on semantic search, relevance prediction, and learning-to-rank.
• You develop and improve ML services for retrieval, ranking, query understanding, and classification.
• Hybrid search solutions combine lexical retrieval, embeddings, neural models, and LLM-based components.
• Together with the team, you will transform prototypes into production-ready services – using technologies such as Python, FastAPI, Docker, PyTorch and vector databases.
• For efficient prototyping, testing, and continuous improvement, you use modern AI-supported and agentic engineering workflows.

What we offer you

Development and responsibility

• Your commitment pays off – we foster your talent and offer opportunities to quickly advance your career.
• Take ownership of your topics, contribute your own ideas, try out new approaches and gradually grow into responsibility for productive search and ranking systems.
• Benefit from internal training with specialized coaches as well as an annual budget for external professional development.

Team spirit and a modern working environment

• Experience team spirit in everyday work and beyond – during shared lunches, a round of table football or after-work activities, and celebrate successes at regular company and team events.
• Work in an inspiring environment with a modern office and high-quality equipment such as MacBooks and height-adjustable desks.

Flexibility and balance

• Working from home on Fridays is optional – those who spend the day in the office accumulate additional vacation days beyond the 28 days.
• Get to the office comfortably with your free Germany ticket or a subsidized company bicycle.
• Enjoy a fresh, free lunch twice a week and take the opportunity to network with colleagues.
• Stay active with our in-house sports classes or take advantage of our subsidized external sports program, including the EGYM Wellpass.