Senior AI Engineer (LLM)

Location: Warsaw/Cracow (hybrid: 1-2 days per week in the office)

Contract: B2B

Salary: 25.000 - 33.000 PLN net B2B

How 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 systems
• Building LLM-powered applications that interact with real users
• Developing and maintaining production Python services
• Exposing 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 quality
• Scaling systems to handle **enormous volumes of requests

Biggest challenges in this role:**

• Greenfield project built from scratch
• High-scale, user-facing systems with strict performance and reliability requirements
• Designing systems meant for long-term ownership, not short-term delivery
• Balancing model quality, latency, and cost in production LLM systems

What you’ll learn:

• How to build LLM-powered products from scratch and take them to production
• Proven approaches to running LLMs in production at scale
• How to design, evaluate, and evolve NLP systems used by real users
• Best practices for **production ML and AI system architecture

What you’ll get to try and experiment with:**

• End-to-end ownership of LLM-based systems
• Optimizing retrieval models, RAG pipelines, and inference workflows
• Experimenting with different LLMs, prompting strategies, and system designs
• Solving performance and reliability challenges under heavy traffic

Core requirements:

• At least 4 years of experience in ML / AI engineering
• Proven experience owning production NLP or LLM systems
• Strong 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 environments
• Hands-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 integrations
• Experience 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 systems
• Python proficiency with experience building and maintaining reliable production services and data pipelines
• Strong software engineering mindset, including code quality, testing, scalability, and production deployments
• Experience building RESTful APIs (FastAPI, Flask) to expose ML/LLM capabilities
• Curiosity and commitment to continuous learning in the NLP/LLM/AI space
• Collaborative team-player with strong communication skills

You will earn extra points for experience with:

• MLOps practices and tooling
• RAG systems, vector databases, and retrieval optimization
• multiple LLM providers or open-source models
• **high-traffic, high-availability systems

We want to offer you:**

• Work with an experienced team that continually shares knowledge and is not afraid of testing new solutions
• Flexible hours
• Individual work tools – Macbook Pro, Dell screen, JBL headphones? You can tailor the equipment to your needs
• Sport & wellness benefit (Kafeteria MyBenefit)
• Private medical care
• A comprehensive benefits package after transitioning to our partner, including employee benefits, training opportunities, and occasional bonuses