Senior Full Stack Engineer - Core UX

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior Full Stack Engineer - Core UX based in Spain. This remote role offers the opportunity to improve the everyday experience of users working with sophisticated, business-critical software. As part of a Core UX-focused engineering team, you will refine existing functionality, strengthen consistency, and deliver polished, high-performing interfaces. You will combine strong frontend expertise with full-stack engineering skills to solve challenging product and technical problems. Working alongside full-stack, data, ML, and DevOps engineers, you will contribute to scalable solutions within a highly collaborative global environment. The role provides substantial ownership, with individual contributions directly influencing both product quality and business outcomes. It is particularly suited to an engineer who enjoys iterative improvement, experimentation, and delivering a premium user experience.

Refine and improve existing product functionality with a strong focus on usability, consistency, responsiveness, performance, and visual quality. Build and maintain scalable full-stack solutions that support reliable, high-quality user experiences. Implement thoughtful frontend interactions and layouts while ensuring a cohesive experience across the product. Collaborate with full-stack, data, machine learning, and DevOps engineers to develop and evolve product capabilities. Contribute to system design, debugging, performance improvements, and technical problem-solving across the application stack. Take full ownership of assigned projects, driving initiatives from initial concept through implementation and completion with minimal oversight. Experiment with different technical and product approaches, measure outcomes, and iterate quickly to improve functionality and user impact. Communicate proactively with stakeholders, surface blockers, ask relevant questions, and provide clear updates throughout projects. Contribute to scalable cloud-based architectures, asynchronous workflows, and reliable backend solutions as the product continues to grow. Requirements: 5+ years of professional software engineering experience, ideally with a strong track record of improving and polishing product functionality and user experiences. Strong engineering fundamentals in system design, debugging, architecture, and problem-solving. Professional experience with a modern frontend framework, preferably React. Strong programming experience with JavaScript, TypeScript, or Python; candidates with strong object-oriented programming backgrounds may also be considered. Experience with cloud and serverless technologies such as AWS Lambda and EC2, as well as asynchronous workflows and cloud-based environments. Comfortable working with relational databases, ideally PostgreSQL. Strong ownership mindset, with the ability to independently drive projects through completion and maintain high standards of quality. Proactive and transparent communication style, with the ability to collaborate effectively in a distributed international environment. Comfortable experimenting, testing ideas, measuring results, and iterating rapidly on complex or unfamiliar problems. Experience with LLMs, generative AI, or distributed systems is a plus. Ability to work from a European country where you are authorized to work; the engagement is offered on a B2B or contractor basis, with no visa sponsorship available. Benefits: Salary range of approximately $80,000–$165,000 USD, depending on experience, performance, and geographic location. Significant equity options package. 20 days of paid time off per year. Opportunity to work with an ambitious, international, and multidisciplinary team on technology addressing a major global industry. Global team offsites and opportunities to connect with colleagues internationally. Phone reimbursement. Gym reimbursement. Student stipend. High level of ownership and the opportunity to make a substantial impact within a growth-stage environment.

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