Senior AI Engineer (LLM)

Location: Warsaw/Cracow (hybrid: 1-2 days per week in the office)Contract: B2BSalary: 25.000 - 33.000 PLN net B2BHow this role works:You will start by building the system as part of our team, working in a focused, greenfield setup. After a few months of introduction to the project, you will seamlessly continue working on the same product directly with the client, becoming part of the client’s team responsible for its long-term development and scaling. There is no handover phase and no context switching - you stay with the same codebase, product, and technical challenges, while gaining long-term ownership and impact.What you’ll work on:Designing, implementing, and deploying end-to-end NLP and deep learning systemsBuilding LLM-powered applications that interact with real usersDeveloping and maintaining production Python servicesExposing models and pipelines via REST APIs (FastAPI, Flask)Working on retrieval models and techniques (RAG, embeddings, ranking)Evaluating, monitoring, and continuously improving model and system qualityScaling systems to handle enormous volumes of requestsBiggest challenges in this role:Greenfield project built from scratchHigh-scale, user-facing systems with strict performance and reliability requirementsDesigning systems meant for long-term ownership, not short-term deliveryBalancing model quality, latency, and cost in production LLM systemsWhat you’ll learn:How to build LLM-powered products from scratch and take them to productionProven approaches to running LLMs in production at scaleHow to design, evaluate, and evolve NLP systems used by real usersBest practices for production ML and AI system architectureWhat you’ll get to try and experiment with:End-to-end ownership of LLM-based systemsOptimizing retrieval models, RAG pipelines, and inference workflowsExperimenting with different LLMs, prompting strategies, and system designsSolving performance and reliability challenges under heavy trafficCore requirements:At least 4 years of experience in ML / AI engineeringProven experience owning production NLP or LLM systemsStrong understanding of Transformer architecture and deep learning foundations behind modern LLMs (attention mechanisms, self-attention, positional encoding, encoder–decoder vs decoder-only models)Proven experience designing, fine-tuning, and deploying end-to-end NLP and deep learning solutions in production environmentsHands-on experience building LLM-powered production systems (e.g. GPT, Claude, Gemini), including prompt engineering, evaluation, supervised fine-tuning (SFT), instruction tuning, and parameter-efficient fine-tuning methods (e.g. LoRA, adapters), as well as user-facing integrationsExperience training and fine-tuning Transformer-based models using frameworks such as PyTorch and Hugging Face (including dataset preparation, tokenization strategies, hyperparameter tuning, and evaluation pipelines)Strong understanding of scalability, performance optimization, and system design for large-scale ML/LLM systemsPython proficiency with experience building and maintaining reliable production services and data pipelinesStrong software engineering mindset, including code quality, testing, scalability, and production deploymentsExperience building RESTful APIs (FastAPI, Flask) to expose ML/LLM capabilitiesCuriosity and commitment to continuous learning in the NLP/LLM/AI spaceCollaborative team-player with strong communication skillsYou will earn extra points for experience with:MLOps practices and toolingRAG systems, vector databases, and retrieval optimizationmultiple LLM providers or open-source modelshigh-traffic, high-availability systemsWe want to offer you:Work with an experienced team that continually shares knowledge and is not afraid of testing new solutionsFlexible hoursIndividual work tools – Macbook Pro, Dell screen, JBL headphones? You can tailor the equipment to your needsSport & wellness benefit (Kafeteria MyBenefit)Private medical careA comprehensive benefits package after transitioning to our partner, including employee benefits, training opportunities, and occasional bonuses