AI Software Engineer
Models, Prompts & Infra — Early-Stage
📍
Barcelona HQ — Hybrid (Tues & Thurs in the office)
💰
€90K base · Competitive Stock Options · Private Health Insurance
🚀
Help us reinvent how careers grow, powered by AI.
The opportunity
At Pensero.ai, every hire moves the needle and in AI, the needle is the product.
We’re looking for one exceptional AI Engineer to take ownership of our models, prompts, infrastructure, evaluation pipelines, and datasets.
You’ll work in tight, iterative cycles, turning messy real-world problems into AI-powered features that are reliable, measurable, and ship fast.
This isn’t a “research-only” role. You’ll move between prompt design, fine-tuning, model selection, eval framework building, and production deployment, often in the same week. You’ll see your work in the hands of users within days, not months, and will shape how AI works inside Pensero for years to come.
What you'll do
Own the AI pipeline end-to-end: from prompt design to model deployment, making sure every step is measurable, reproducible, and production-ready.
Select & integrate the right models: open-source models balancing speed, accuracy, cost, and maintainability.
Design and maintain evaluation frameworks so we know exactly when a model, prompt, or dataset change is an improvement.
Build and manage AI infrastructure: fine-tuning workflows, inference APIs, for scale and reliability.
Curate and generate datasets for training, testing, and benchmarking, including building the tooling to automate this.
Collaborate directly with product & engineering to decide not just how to implement AI features, but which ones we should build in the first place.
Ship, learn, repeat: deploy to production quickly, monitor, and iterate based on real-world feedback.
Bonus points for…
Experience in AI beyond just LLMs — embeddings, retrieval, fine-tuning, multimodal models.
Hands-on work with LLMOps: prompting, RAG pipelines, evaluation, guardrails.
Knowledge of vector DBs (e.g., Weaviate, Milvus, Pinecone) and search/retrieval systems.
Building and running eval pipelines that mix automated metrics and human feedback.
Familiarity with hybrid model setups — mixing self-hosted and provider-based.
Contributions to open-source AI projects.
Ideas from adjacent fields (search, NLP, distributed systems) that could sharpen our approach.
Compensation and perks
€90K base salary: competitive for early-stage, senior-level roles in Barcelona.
Generous stock options: real ownership in the company you’re helping to build.
Private health insurance: because your well-being matters as much as your work.
A say in key product and company decisions: not just your code.
Hiring process
Portfolio review — If you have GitHub or other public work, we’d love to see it.
Intro call (30 min) — quick mutual fit check.
Practical exercise (less than 3 hours) — tailored to your experience. Use AI if it helps — we encourage it.
Review & discussion (1 hour) — we go through your work together, just like we would as teammates.
Technical deep dive (1 hour) — architecture, trade-offs, and problem-solving approach.
Values interview — 15 mins casual chat with two team members, then 30 min with a co-CEO.
Offer — clear, fast, and respectful of your decision-making process.
