Senior AI Engineer

Lexroom Srl; Barcelona; Hybrid; EUR 70,000 - 100,000; Full time

Benefits offered by this job

Hybrid work Barcelona office

Health coverage

Meal vouchers

Performance bonuses

Team retreats & off-sites

Equity package

Job summary

Lexroom.ai, a Barcelona-based AI company building a legal platform, seeks an experienced ML engineer to design and optimize agent-driven, RAG-based AI systems for complex legal tasks. You'll fine-tune LLMs, develop large-scale search pipelines, and work with legal experts to build reliable, domain-specific data.

The role offers hybrid work, equity, and a competitive salary package. Join a fast-growing team delivering measurable impact on how legal professionals work—faster, clearer, and more

Qualifications

• Proven expertise in building and managing robust ML pipelines.
• Strong Python skills with LLM research experience.
• Knowledge of full-text search, vector databases, or large-scale retrieval systems.
• Collaborative mindset to work with legal experts, researchers and engineers.
• Familiarity with MLOps and production backends.
• Up-to-date with LLM innovation and practical deployment.
• Fluent English; Italian a plus.

Responsibilities

• Design and build agent-driven and RAG-based AI systems for complex legal tasks.
• Fine-tune and post-train LLMs using supervised and RL methods to improve quality.
• Develop and optimize large-scale search pipelines for LLM-powered agents.
• Implement NLP algorithms to extract, structure, and validate information from legal documents.
• Run end-to-end evaluations to identify bottlenecks and drive improvements.
• Collaborate with legal experts to design evaluation protocols and build datasets.
• Maintain technical excellence with best practices and code reviews.

Skills

ML pipelines

Python

Search technologies

Collaboration

MLOps

LLM innovation

English fluency

Italian (nice-to-have)

Tools

Vector databases

Full-text search

Job description

Lexroomis building the AI platform where legal work gets done. In just over two years, we've grown from zero to €25M ARR, and today more than 20,000 legal professionals across Italy, Spain, Germany, France, and Bulgaria rely on Lexroom.
We're backed by $73M from Left Lane Capital, Base10 Partners, and Eurazeo, and we're a team of around 300 builders who move fast, say things straight, and own each outcome.
Our next goal? Become Europe's most-used legal product.

Why Lexroom?

• Shape the Standard: Be part of the team setting the benchmark for legal AI in Europe.

• Work with the Best: Collaborate with exceptional colleagues in a culture that values competence, curiosity, and ambition.

• Deliver Meaningful Results: Your contribution will directly influence how legal professionals work—faster, clearer, and more efficiently.

At Lexroom, we leave buzzwords behind. Here, you’ll build something that lasts: a trusted platform, a strong reputation, a new standard for the legal world.

What You'll Do

• Design and build agent-driven and RAG-based AI systems to solve complex legal tasks with precision and efficiency.

• Fine-tune and post-train LLMs using cutting-edge supervised and reinforcement learning techniques to raise response quality.

• Develop and optimize large-scale search pipelines for LLM-powered agents.

• Implement and refine NLP algorithms to extract, structure, and validate information from legal documents.

• Run end-to-end evaluations to pinpoint bottlenecks, measure performance, and guide continuous improvements.

• Work closely with legal experts to design evaluation protocols and build reliable, domain-specific datasets that strengthen every layer of the stack.

• Maintain technical excellence by following established best practices, coding standards, and rigorous code-review processes.

What You’ll Bring

• Proven expertise in building and managing robust ML pipelines.

• Strong Python skills with hands-on experience in LLM research and deep learning systems.

• Knowledge of search technologies such as full-text search, vector databases, or other large-scale retrieval systems.

• Collaborative mindset and readiness to work with legal experts, researchers, and engineers to keep improving the product.

• Familiarity with MLOps and integrating ML models into production backends (a strong plus).

• Up-to-date with LLM innovation, ideally with experience in pre-training or deploying large-scale models in real-world scenarios.

• Fluency in English, both written and spoken, knowledge of Italian is a plus.

What Sets Us Apart

An Exceptional Team.

At Lexroom.ai, you’ll work alongside top talent in tech and legal AI.

Our focused teams operate with purpose and autonomy, so every contribution delivers visible results.

You’ll collaborate with people who pair innovation with rigor, curiosity with discipline, ambition with depth.

Growth that Matters.

We hire exceptional people to make a difference—and we give them space to lead.

As we scale, your work will shape the future of legal technology and set new standards for the field.

Impact is defined by vision and execution, not by age or title. If you’re ready to take responsibility, you’ll find real opportunities to grow and lead high-stakes projects.

Rewarding Your Contribution.

We value excellence and share success:

• Annual Salary Range: €70,000 – €100,000

• Equity Package: Align your growth with the company’s long-term success.

Benefits That Matter

• Hybrid Work: Flexibility to balance remote work with in-person collaboration at our Barcelona office.

• Health Coverage: Comprehensive insurance to keep you secure and focused.

• Meal Vouchers: Daily support for your lunch breaks.

• Performance Bonuses: Rewards directly tied to measurable results.

• Team Retreats & Off-sites: Dedicated time to connect, collaborate, and spark bold ideas.

**At Lexroom.ai, ambition meets discipline and purpose.

We’re not just building a product—we’re setting a new standard for the legal world. If you’re ready to contribute to something lasting and meaningful, we’d love to hear from you.**