Senior Full Stack Engineer - Core UX

📍 Job Overview

Job Title: Senior Full Stack Engineer - Core UX

Company: Jobgether (Partner Company)

Location: Spain

Job Type: Full-time, Contractor

Category: Software Engineering / Core UX

Date Posted: September 04, 2026

Experience Level: 5-10 Years Professional Experience

Remote Status: Remote OK (within Spain)

🚀 Role Summary

• This role focuses on enhancing the core user experience (UX) of sophisticated software and AI-powered solutions within a global engineering team.

• Responsibilities include refining existing product functionality for consistency, responsiveness, performance, and visual polish, directly impacting daily user interactions.

• The position requires strong full-stack engineering skills to deliver scalable and reliable solutions, combining frontend expertise with backend development.

• Collaboration is key, working closely with full-stack, data, machine learning, and DevOps engineers in a highly collaborative, distributed environment.

• This is an opportunity for an experienced engineer to take end-to-end ownership and drive significant product and business influence within a small, high-performing team.

📝 Enhancement Note: While the title is "Senior Full Stack Engineer - Core UX," the description emphasizes deep involvement in user experience refinement and product polish. This suggests a role that bridges traditional full-stack development with a strong product design and user-centric engineering focus, rather than purely backend or frontend specialization. The "Core UX" aspect implies a foundational role in shaping the user's interaction with the platform.

📈 Primary Responsibilities

• Enhance existing product functionality with a primary focus on usability, consistency, responsiveness, performance, and visual quality.

• Improve the overall user experience through meticulous attention to layouts, interactions, interface behavior, and product polish.

• Design, develop, debug, and maintain scalable full-stack solutions to support evolving product requirements.

• Contribute significantly to frontend development, leveraging modern frameworks, with a preference for React expertise.

• Develop and maintain backend functionality, including serverless architectures, asynchronous workflows, and cloud-based services.

• Design and implement reliable, scalable data solutions, working effectively with relational databases.

• Collaborate proactively with a globally distributed team of full-stack, data, machine learning, and DevOps engineers.

• Take end-to-end ownership of projects, driving initiatives from problem definition through implementation and completion with minimal supervision.

• Communicate progress, identify and surface blockers, ask thoughtful questions, and keep relevant stakeholders informed.

• Experiment with new approaches, measure results, and iterate rapidly to solve complex or novel technical and product challenges.

• Contribute to a culture that emphasizes high standards, customer impact, transparency, accountability, continuous experimentation, and technical excellence.

📝 Enhancement Note: The responsibilities highlight a blend of tactical execution (refining functionality, developing solutions) and strategic contribution (taking ownership, driving initiatives, experimenting). The emphasis on "end-to-end ownership" and "minimal oversight" indicates a senior-level expectation for autonomy and project leadership within the Core UX domain.

🎓 Skills & Qualifications

Education: Not explicitly specified, but professional experience is heavily weighted.

Experience: 5+ years of professional software engineering experience, with a strong track record of improving and polishing product functionality to deliver a premium user experience.

Required Skills:

• Strong software engineering fundamentals, including system design, debugging, architecture, and structured problem-solving.

• Professional experience with a modern frontend framework, preferably React.

• Strong knowledge of JavaScript, TypeScript, and/or Python; equivalent experience in other object-oriented programming languages will be considered.

• Experience with serverless technologies and cloud environments (e.g., AWS Lambda, EC2).

• Experience designing or working with asynchronous workflows and scalable backend systems.

• Solid experience with relational databases, ideally PostgreSQL.

• Exceptional attention to detail and a genuine appreciation for high-quality, polished user experiences.

• Demonstrated ownership, initiative, resilience, and the ability to drive projects forward independently.

• Excellent communication skills and a proactive approach to collaboration in a distributed, cross-functional environment.

• Comfort experimenting, measuring outcomes, learning quickly, and iterating on challenging problems.

• Ability to thrive in a fast-paced growth environment with ambitious goals and a high degree of responsibility.

• Authorization to work in the European country where you are based (Spain). Preferred Skills:

• Experience with LLMs, generative AI, or distributed systems.

📝 Enhancement Note: The requirements lean heavily on practical experience and demonstrated skill rather than formal education. The preference for React, JavaScript/TypeScript, Python, AWS, and PostgreSQL aligns with modern full-stack development stacks, especially in cloud-native environments. The "Core UX" aspect is reinforced by the strong emphasis on attention to detail and appreciation for polished user experiences.

📊 Process & Systems Portfolio Requirements

Portfolio Essentials:

• Showcase of projects demonstrating end-to-end ownership and impact on user experience and product polish.

• Examples of refined product functionality, highlighting improvements in usability, consistency, responsiveness, and performance.

• Code samples or case studies illustrating full-stack development of scalable solutions, including frontend (React) and backend (serverless, cloud).

• Demonstrations of work with relational databases (e.g., PostgreSQL) and asynchronous workflows.

• Evidence of proactive problem-solving, iterative development, and measurement of results. Process Documentation:

• Case studies detailing how complex or novel technical/product challenges were approached, experimented with, and solved.

• Examples of contributions to a culture of high standards, customer impact, transparency, accountability, and continuous experimentation.

• Documentation of collaboration within distributed, cross-functional teams.

📝 Enhancement Note: While a formal portfolio isn't explicitly mandated, the job description strongly implies that candidates will need to demonstrate their capabilities through project examples, code contributions, or detailed case studies during the interview process. The focus will be on showcasing practical application of skills in a way that highlights user experience impact and end-to-end ownership.

💵 Compensation & Benefits

Salary Range: $80,000 to $165,000 USD per year.

Explanation: This range is provided by the employer and is dependent on experience, performance, and geographic location. Given the role is based in Spain, the upper end of the range likely reflects senior-level expertise and potentially higher cost-of-living areas within Spain, while the lower end is for candidates with strong foundational experience meeting the senior criteria. The currency is USD, which is common for international tech roles or contractor arrangements.

Benefits:

• Significant equity options package.

• 20 days of paid time off per year.

• Global team offsites for international connection and collaboration.

• Phone reimbursement.

• Gym reimbursement.

• Student stipend.

• Opportunity to work with ambitious, highly skilled professionals across various engineering disciplines.

• Significant individual impact within a small, high-performing team.

• Opportunity to work on challenging technology and AI problems.

• An environment emphasizing ownership, experimentation, transparency, continuous learning, and measurable customer impact.

Working Hours: Approximately 40 hours per week. The role is remote within Spain, allowing for flexibility in daily scheduling, but core working hours for collaboration across distributed global teams will likely apply.

📝 Enhancement Note: The salary range is competitive for senior full-stack engineering roles, particularly for remote positions in Spain, even when denominated in USD. The benefits package is robust, including equity, generous PTO, and support for professional and personal well-being, which are attractive to experienced engineers. The mention of "contractor arrangement" in the requirements alongside "full-time" employment type suggests the possibility of either a direct employee role or a B2B contractor setup, which might affect local employment terms.

🎯 Team & Company Context

🏢 Company Culture

Industry: Software & AI Solutions for a Complex, High-Impact Industry.

Company Size: Not explicitly stated, but described as a "small, high-performing team" and a "fast-paced growth environment." This suggests a dynamic startup or a focused division within a larger organization.

Founded: The founding date is not provided.

Team Structure:

• A global engineering team comprising full-stack, data, machine learning, and DevOps engineers.

• The "Core UX" team is a small, high-performing unit within this larger structure.

• Collaboration is emphasized across these disciplines.

• The role implies a flat or semi-flat hierarchy where individual contributions have significant influence. Methodology:

• Data-driven decision-making and continuous experimentation.

• Iterative development with rapid learning and adaptation.

• Emphasis on high standards, customer impact, transparency, and accountability.

• Agile methodologies are likely employed given the fast-paced growth environment.

Company Website: jobgether.com (though the role is for a partner company, Jobgether manages the application process).

📝 Enhancement Note: The company culture is described as highly performance-oriented, emphasizing technical excellence, user impact, and continuous improvement. The "small, high-performing team" aspect suggests a close-knit unit where individual contributions are highly visible and impactful. The global, distributed nature of the team requires strong asynchronous communication skills and self-discipline.

📈 Career & Growth Analysis

Operations Career Level: Senior Full Stack Engineer - Core UX. This level implies a high degree of autonomy, technical leadership, and the ability to mentor junior engineers. The focus on "Core UX" suggests a specialization within the broader engineering function, contributing directly to product quality and user satisfaction.

Reporting Structure: The role reports into the Core UX team lead or engineering management within the partner company. Collaboration is expected with cross-functional teams, including data scientists and ML engineers, indicating a matrixed reporting or strong cross-functional alignment.

Operations Impact: The role has a direct and significant impact on the core user experience of the product. By refining usability, consistency, and performance, this engineer influences user adoption, retention, and overall product satisfaction, which in turn drives business outcomes. Decisions made by this senior engineer will have substantial influence on both the product's technical direction and its market success.

Growth Opportunities:

• Technical Specialization: Deepen expertise in frontend frameworks (React), backend technologies, serverless architectures, and potentially AI/LLM integration.

• Leadership Development: Potential to move into Tech Lead roles within the Core UX team or other engineering domains, guiding project execution and mentoring engineers.

• Cross-functional Expertise: Gain exposure to data science, machine learning, and DevOps practices, broadening skill sets and understanding of the full product lifecycle.

• Product Influence: Contribute to product strategy and roadmap through user experience insights and technical feasibility assessments.

• Continuous Learning: The environment encourages experimentation and rapid learning, fostering ongoing professional development.

📝 Enhancement Note: This is a senior individual contributor role with significant potential for growth. The emphasis on "Core UX" suggests a path towards specialized product engineering leadership, focusing on the intersection of technical implementation and user-centric design. The "fast-paced growth environment" hints at opportunities for rapid advancement as the company scales.

🌐 Work Environment

Office Type: Remote within Spain. The role is offered through a B2B or contractor arrangement, indicating the primary work setting is home-based.

Office Location(s): Spain. Specific city details are not provided, but the role requires authorization to work in the European country where the candidate is based.

Workspace Context:

• A fully remote work environment within Spain, offering flexibility in daily work arrangements.

• Collaboration occurs primarily through digital tools (e.g., Slack, video conferencing), requiring strong asynchronous communication skills.

• Access to modern development tools and cloud infrastructure is implied given the technical requirements.

• The distributed global team structure means interaction with colleagues across different time zones is expected.

Work Schedule: Approximately 40 hours per week. While remote, core collaboration hours will likely be established to facilitate team synchronization and project alignment across the distributed global team.

📝 Enhancement Note: The remote nature of the role in Spain offers flexibility, but candidates must be self-motivated and adept at remote collaboration. The need to work with a global team suggests that some flexibility in working hours might be necessary to accommodate different time zones for meetings and synchronous communication.

📄 Application & Portfolio Review Process

Interview Process:

• AI-Powered Screening: Initial application review via Jobgether's AI system to assess core requirements objectively.

• Shortlisting: Top-fitting candidates are shortlisted and shared with the hiring company.

• Company-Managed Interviews: The partner company will manage subsequent interview stages, which typically include:

  • Technical Screening: Assessment of core engineering fundamentals, system design, and problem-solving skills. This may involve live coding or whiteboard exercises.
  • Core UX Deep Dive: Discussion focused on user experience principles, attention to detail, and how candidates approach product polish and refinement.
  • Full-Stack Project Discussion: In-depth review of past projects, focusing on full-stack architecture, technology choices, and end-to-end ownership. Candidates may be asked to present specific projects from their portfolio.
  • Behavioral & Cultural Fit: Evaluation of ownership, initiative, resilience, communication, and alignment with the company's values (high standards, customer impact, experimentation, transparency, accountability).
  • Final Rounds: Potentially with senior leadership or hiring managers to discuss strategic alignment and role expectations.

Portfolio Review Tips:

• Showcase Impact: Highlight projects that demonstrate a clear impact on user experience, product polish, or key business metrics. Quantify results whenever possible.

• Detail Process: Explain your thought process for design decisions, problem-solving approaches, and how you iterated to achieve the final outcome.

• Technical Depth: Be prepared to discuss the technical architecture, trade-offs considered, and specific implementation details of your projects.

• UX Focus: For this role, emphasize projects where you had a significant hand in user-facing features, interface design, responsiveness, and performance optimization.

• Ownership Narrative: Clearly articulate your role and level of ownership in each project.

Challenge Preparation:

• System Design: Review common system design principles, scalability patterns, and trade-offs for building robust applications.

• Frontend Challenges: Practice with common React component design, state management, and performance optimization scenarios.

• Problem-Solving Scenarios: Prepare to tackle abstract or concrete technical problems, demonstrating structured thinking and effective communication of your solution.

• UX Principles: Brush up on fundamental UX principles, usability heuristics, and best practices for creating intuitive and polished interfaces.

📝 Enhancement Note: The application process leverages AI for initial screening, emphasizing the importance of a well-structured resume and clear alignment with the core requirements. Candidates should anticipate rigorous technical and behavioral interviews, with a strong focus on demonstrating practical experience in full-stack development and UX refinement, supported by concrete project examples.

🛠 Tools & Technology Stack

Primary Tools:

• Frontend: Modern JavaScript/TypeScript frameworks, with a strong preference for React.

• Backend: Serverless technologies (e.g., AWS Lambda), asynchronous workflows, cloud-based services.

• Databases: Relational databases, ideally PostgreSQL.

• Cloud Platforms: Experience with cloud environments, specifically AWS (EC2 mentioned).

• Programming Languages: JavaScript, TypeScript, Python, or equivalent object-oriented languages.

Analytics & Reporting: While not explicitly mentioned, a role focused on UX and product polish in a growth environment would likely involve using analytics tools for user behavior tracking and A/B testing to measure impact.

CRM & Automation: Not specified for this role, as it's an engineering position.

📝 Enhancement Note: The technology stack is modern and geared towards scalable, cloud-native applications. Proficiency in React, JavaScript/TypeScript, Python, AWS, and PostgreSQL are key technical indicators for this role. The emphasis on serverless and asynchronous workflows points towards a microservices or event-driven architecture.

👥 Team Culture & Values

Operations Values:

• High Standards: Commitment to craftsmanship, code quality, and delivering polished, premium user experiences.

• Customer Impact: Focus on how technical decisions translate into tangible benefits for users and the business.

• Transparency: Open communication about progress, blockers, and decision-making processes.

• Accountability: Taking ownership of projects and outcomes, driving initiatives to completion.

• Continuous Experimentation: Willingness to try new approaches, measure results, and learn from outcomes.

Collaboration Style:

• Highly collaborative within a distributed, cross-functional team environment.

• Proactive communication, asking thoughtful questions, and keeping stakeholders informed.

• Emphasis on shared ownership and collective problem-solving.

• Respect for diverse technical perspectives within engineering, data, and ML disciplines.

📝 Enhancement Note: The company culture appears to be a strong driver for this role. Candidates should demonstrate alignment with these values, particularly in their approach to problem-solving, teamwork, and commitment to quality and innovation.

⚡ Challenges & Growth Opportunities

Challenges:

• Balancing Polish and Pace: Delivering a highly polished UX in a fast-paced growth environment requires efficient development and prioritization strategies.

• Distributed Collaboration: Effectively communicating and collaborating with a global, remote team across different time zones.

• Complex Technical Problems: Tackling challenging technical and product issues, potentially involving AI/LLM integration, with limited oversight.

• End-to-End Ownership: Managing projects from inception to completion, requiring strong self-discipline and project management skills.

Learning & Development Opportunities:

• Advanced Technical Skills: Deepen expertise in modern full-stack development, cloud-native architectures, and potentially AI/ML technologies.

• Product Strategy Input: Contribute to product roadmap and design decisions based on UX expertise and technical feasibility.

• Leadership and Mentorship: Opportunity to grow into technical leadership roles, guiding teams and mentoring junior engineers.

• Industry Exposure: Work on cutting-edge AI and software solutions within a high-impact industry.

📝 Enhancement Note: This role offers significant opportunities for professional growth by tackling complex challenges in a dynamic environment. The company seems to foster a culture where learning and development are integral to the work itself.

💡 Interview Preparation

Strategy Questions:

• "Describe a time you significantly improved the user experience of a product. What was your process, and what were the measurable outcomes?" (Focus on UX impact, detail, and metrics).

• "Walk us through the architecture of a complex full-stack application you built or significantly contributed to. What trade-offs did you make, and why?" (Focus on system design, scalability, and technical rationale).

• "How do you approach balancing the need for product polish with rapid development cycles in a startup environment?" (Focus on prioritization, efficiency, and pragmatism).

• "Describe a challenging technical problem you encountered and how you solved it. What did you learn from the experience?" (Focus on problem-solving methodology, resilience, and learning). Company & Culture Questions:

• "What excites you about working on the 'Core UX' of a product?" (Assess passion for user experience and product quality).

• "How do you contribute to a culture of high standards and continuous experimentation?" (Evaluate alignment with company values).

• "Describe your experience working in a distributed, cross-functional team. How do you ensure effective collaboration?" (Assess communication and teamwork skills). Portfolio Presentation Strategy:

• Focus on Impact: Select 2-3 key projects that best showcase your full-stack capabilities and your contributions to core UX and product polish.

• Tell a Story: For each project, clearly articulate the problem, your role and approach, the technical solutions implemented, and the resulting impact (quantify if possible).

• Highlight UX Elements: Specifically point out how you addressed usability, consistency, responsiveness, and visual quality in your chosen projects.

• Be Ready for Deep Dives: Prepare to discuss technical details, architectural decisions, and trade-offs in depth.

📝 Enhancement Note: Interview preparation should focus on demonstrating both strong technical acumen and a deep understanding of user experience principles. Candidates should be ready to articulate their thought process, showcase ownership, and align their experiences with the company's values of quality, experimentation, and customer impact.

📌 Application Steps

To apply for this Senior Full Stack Engineer - Core UX position:

• Submit your application through the Jobgether platform.

• Tailor your resume: Highlight your 5+ years of professional software engineering experience, emphasizing full-stack development, React expertise, and specific contributions to product polish and user experience improvement. Integrate keywords from the job description like "React," "TypeScript," "AWS Lambda," "PostgreSQL," "system design," and "user experience."

• Prepare your portfolio: Select 2-3 impactful projects that demonstrate your full-stack skills and your ability to refine user experiences. Be ready to discuss these projects in detail, focusing on the problem, your solution, and the impact.

• Practice interview responses: Rehearse answers to common technical, behavioral, and situational questions, particularly those related to UX, product polish, system design, and remote collaboration.

• Research the company (if possible): While the role is for a partner company, understanding Jobgether's mission and AI-powered matching process can provide context. Focus your research on the partner company's industry and any publicly available information about their product and engineering culture.

⚠️ Important Notice: This enhanced job description includes AI-generated insights and operations industry-standard assumptions. All details should be verified directly with the hiring organization before making application decisions.