Senior Research Scientist | Model Scaling

Meet DeepL. DeepL is a global AI product and research company focused on building secure, intelligent solutions to complex business problems. Over 200,000 business customers and millions of individuals across 228 global markets today trust DeepL's Language AI platform for human-like translation, improved writing, and real-time voice translation.

Founded in 2017 by CEO Jaroslaw “Jarek” Kutylowski, DeepL now has around 1,000 passionate employees and is supported by world-renowned investors including Benchmark, IVP, and Index Ventures. Our goal is to become the global leader in trusted, intelligent AI technology, building products that drive better communication, foster connections, and create a meaningful impact. To achieve this, we need talented people like you to join our journey.

What sets us apart is our blend of cutting-edge AI technology, meaningful work, and a culture where people truly thrive. We’re a team of innovators, researchers, and creators driven by a shared purpose to unlock human potential by making work simpler, smarter, and more connected. When we share what it’s like to work at DeepL, the reactions are overwhelmingly positive. This might be because of our technology that helps millions of people and businesses communicate and work better every day, or because of the trust, curiosity, and care that shape our culture. What we know for sure is this: being part of DeepL means joining a team dedicated to innovation, growth, and well-being.

Our Language AI teams form the foundation of DeepL's success. We are a dedicated group of researchers who collaborate closely with engineers, product managers, and designers. Our mission is to build the world's leading language AI system to deliver perfect translations for the most demanding use cases. To that end, we take responsibility for the entire life cycle of the machine learning models that power our language AI products. This includes data, training, quality assurance, and operational aspects. In our highly collaborative teams, each person has the scope to drive impact across the company.

Your responsibilities include:

• Drive the selection and evaluation of open foundation / open-weight models as the basis for our next-generation translation systems.
• Lead model selection and general architecture decisions for scaling to hundreds of billions of parameters, including Mixture-of-Experts and other sparse or efficient designs.
• Design multi-capability adaptation strategies using LoRA, PEFT, and related methods.
• Own the modelling lifecycle for your work: prototyping, ablations, scaling experiments, evaluation, and delivery into production, with rigorous and reproducible evaluation.
• Partner closely with post-training, RL/RLHF, and instruction-following specialists to integrate alignment and capability work into the base model.
• Stay ahead of the open-model and scaling literature, and bring well-founded recommendations back to the team.

Qualities we look for:

• Strong hands-on experience adapting and scaling large language models via fine-tuning, instruction-tuning, or post-training of multi-billion-parameter models beyond black-box use.
• Sound judgment about architecture trade-offs at scale (e.g. dense vs. MoE) and about which open-weight foundation models to build on.
• Working knowledge of parameter-efficient and multi-capability adaptation (LoRA/PEFT and variants).
• A hands-on builder who enjoys training models, running experiments, and debugging pipelines, and who can carry research results through to production with engineering.
• Strong coding and experimentation skills (Python, PyTorch/JAX/Tensorflow).
• Ability to communicate clearly, collaborate across teams, and align research work with product and engineering priorities.

Nice to have:

• Experience quantifying uncertainty in large models — calibration and confidence estimation via Bayesian methods, ensembling, steering, or prompt-based approaches.
• Experience with machine translation, multilingual NLP, or document-/layout-aware modelling experience.
• Familiarity with MoE-specific training and adaptation (e.g. expert routing, Mixture-of-LoRA-Experts) and large-scale data-mixture design.

What we offer:

• Diverse and internationally distributed team: joining our team means becoming part of a large, global community with people of more than 90 nationalities.
• Open communication, regular feedback: as a language-focused company, we value the importance of clear, honest communication.
• Hybrid work, flexible hours: we offer a hybrid work schedule, with team members coming into the office twice a week.
• Virtual Shares: An ownership mindset in every role.
• Regular in-person team events: we bond over vibrant events that are as unique as our team.
• Monthly full-day hacking sessions: every month, we have Hack Fridays, where you can spend your time diving into a project you're passionate about.
• 30 days of annual leave: we value your peace of mind.
• Competitive benefits: we've crafted it to reflect the diversity of our team and tailored it to align with your unique location.

If this role and our mission resonate with you, but you're hesitant because you don't check all the boxes, don't let that hold you back. At DeepL, it's all about the value you bring and the growth we can foster together. Go ahead, apply—let's discover your potential together. We can't wait to meet you!

We are an equal opportunity employer. You are welcome at DeepL for who you are - we appreciate authenticity here. Our product is for everyone, and so is our workplace. The more voices we have represented and amplified in our business, the more we will all succeed, contribute, and think forward!