Software Engineer (Foundational AI)

Job Description

About the role We're looking for a Foundational AI Engineer to join our AI team, working directly with our co-founder and Chief Science Officer. This role is about building our own models. Rather than working on top of existing models, you'll train, fine-tune, post-train, and evaluate the small and large language models that power Maisa Studio — the capability that lets us run the majority of our clients' workloads on our own models and dramatically reduce the cost and dependency of using frontier providers. It's deep, hands-on model work in Python and PyTorch, with a strong emphasis on evaluation and on getting models into reliable production use inside highly regulated environments — banks, insurers, and telecoms where getting it wrong isn't an option. This is an early-stage company, and the AI team is growing quickly. You'll have real ownership over what we build and how we build it. What you'll do Train, fine-tune, and post-train Maisa's own small and large language models — from data preparation through to evaluation and release Design and run rigorous model evaluation: benchmarks, regression sets, and quality criteria that reflect real client use cases rather than leaderboard scores Build and improve training pipelines and infrastructure, including data curation, experiment tracking, and reproducibility Apply and adapt modern training techniques — parameter-efficient fine-tuning, post-training and alignment methods — and evaluate their real impact Work with our AI infrastructure function on model serving and inference optimisation (vLLM, SGLang), including the constraints of deploying inside client environments Monitor deployed models for quality degradation and drift, and drive the retraining or corrective work required Help shape our model strategy — where custom models genuinely add value versus using frontier models or deterministic code Collaborate closely with our Applied AI, product, and engineering teams to make sure models meet real product and client needs What we're looking for Genuine, current, hands-on experience training and fine-tuning models — this is a builder's role, not a supervisory one Strong PyTorch depth: comfortable building and modifying model architectures directly, not only running existing pipelines Rigorous approach to evaluation — you can explain how you know a model is actually good, and how you'd detect regressions and degradation Solid software engineering fundamentals in Python Sound judgment on when custom models are worth the investment, weighed against accuracy, cost, and latency Comfortable working in a fast-moving, ambiguous environment with a high degree of ownership Strong communication skills — you'll work closely with engineers, product, and leadership Nice to have Experience with model serving and inference optimisation at scale (vLLM, SGLang, quantisation) Experience deploying models in regulated, on-premise, or air-gapped environments Familiarity with the Hugging Face ecosystem (transformers, datasets, PEFT, TRL) Experience with distributed or multi-GPU training Open-source contributions or published work in the ML community Background in an early-stage or scaling startup Location Fully remote. We have offices in Madrid, Barcelona, and Valencia — visiting is entirely optional. Why join Maisa! You will be joining one of Europe’s most exciting early-stage AI start-ups, where you’ll have the opportunity to work with cutting-edge Agentic Process Automation that’s reshaping how enterprises approach AI deployment. You will get to directly influence how major multinational organizations transform critical business processes, working on genuinely differentiated technology that solves real enterprise AI challenges. Following our recent $25m Seed Round, backed by leading Venture Capital firms including Creandum, Forgepoint, NFX, and Village Global, we’re scaling quickly and realising significant enterprise traction. This is your opportunity to help solve real AI enterprise challenges, working alongside deep technical and industry experts, where you will be challenged daily and expedite your learning and development. The Culture is OURS to Create We’re still shaping how we work together—and that’s part of what makes joining Maisa now specifically exciting. Everyone who joins has the opportunity to influence how we collaborate, connect, and build our culture. Rather than inheriting a finished playbook, you’ll have a voice in creating it.