This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior ML Engineer (Token Factory) based in Spain. This role offers the opportunity to work at the forefront of large-scale AI infrastructure and machine learning systems.You will help build inference and fine-tuning technologies for foundation models spanning language, vision, audio, and multimodal architectures.Your work will focus on improving model quality, training efficiency, inference performance, and hardware utilization at massive scale.You will tackle technically challenging problems involving distributed training, low-precision computation, optimization, and reinforcement learning.Working primarily with Python and JAX, you will turn advanced research ideas into reliable, production-ready systems.The role combines deep technical ownership with opportunities to influence engineering practices and contribute to the evolution of AI platforms.You will collaborate with highly experienced engineers and researchers in a fast-moving, international environment where your work can have significant impact.