Full Stack Engineer

AB
On-site
Posted Oct 8, 2026
1 position

€30,000–€50,000 / year

Opens LinkedIn

Employment type: Full-time
Experience level: Senior · 5+ years
Posting language: English
Working hours: 40 hours per week
Seniority: Associate
Application method: Direct apply is available
Work authorization: Visa sponsorship mentioned

Job summary

Build, maintain, and own full-stack software products from development through long-term production quality, working with Product Owners to turn business needs into technical solutions. Make architecture and engineering decisions, use AI coding agents and modern testing practices, and help establish engineering standards as the team grows.

Job details

Full-Stack Engineer (Junior & Senior Levels) Build AI Products. Own Them. Shape the Future of Engineering in Barcelona. Full-Time | Permanent Location: Barcelona, Spain Open to candidates across North America (United States & Canada) Relocation to Barcelona, Spain is required Visa sponsorship and relocation support available Target Start Date: January 2027 (or as soon as work authorization is completed) About Mainloop Mainloop is a new AI-native engineering team based in Barcelona, built from the ground up inside an established international group. We combine the energy of a startup with the stability, customers, and global reach of an organization that has been operating for decades. Our mission is to build software that transforms how professional-services businesses operate by automating complex processes, reducing administrative work, and creating products that teams rely on every day. The group has operated a technology lab in Casablanca for more than eight years. Barcelona is our second technology hub, created to be closer to the businesses we support and built with AI at the center from the beginning. We are building the team now, and this is an opportunity to help shape how modern engineering teams work. The Opportunity We are hiring Full-Stack Engineers at two levels: Junior Full-Stack Engineers We are looking for early-career engineers who are curious, ambitious, and excited about the future of AI-assisted software development. You do not need years of production experience. What matters is: You can build working applications. You enjoy learning quickly. You have experimented with AI coding tools. You want to become exceptional at building software with modern AI workflows. Senior Full-Stack Engineer We are looking for an experienced engineer who has owned production software and can help define architecture, engineering standards, and development practices as the team grows. You will help shape how products are built, maintained, and scaled. What You Will Do As a Full-Stack Engineer at Mainloop, you will own products from development through long-term success. You will: Build and maintain software products used by teams across multiple countries. Partner with Product Owners to translate business needs into technical solutions. Design scalable architectures and make strong engineering decisions. Develop frontend and backend applications. Review, improve, and maintain existing codebases. Use AI coding agents to accelerate development while maintaining quality. Build features, write tests, and ship reliable software. Own production quality and continuously improve the products you support. Help define engineering practices, tools, and standards as the team grows. AI-Native Engineering Environment Mainloop is not a traditional engineering team that added AI tools afterward. AI is part of how we build from day one. You will work with: AI coding agents such as Claude Code, Cursor, Codex, and similar tools. AI-assisted development workflows. Automated code review processes. Modern testing and deployment practices. Shared engineering patterns across our products. The goal is not simply to write code faster. The goal is to become better engineers by spending more time on: Architecture Problem solving Product decisions Quality Technical judgment What We Are Looking For We are looking for engineers who enjoy ownership and building things that matter. You may be a strong fit if you have: Experience building web applications across frontend and backend. Strong understanding of software engineering fundamentals. Experience with modern development frameworks and technologies. Ability to understand existing codebases and improve them. Interest in AI-assisted development and modern engineering workflows. Strong problem-solving skills and attention to quality. Ability to communicate clearly in English. For the Senior Engineer role, we are looking for: Experience owning production applications. Ability to make architecture decisions. Experience mentoring or guiding other engineers. Strong judgment around technical trade-offs. For the Junior Engineer role, we are looking for: Ability to build a complete working application. Personal projects, internships, university projects, or early professional experience. Curiosity and motivation to grow quickly. Experience experimenting with AI coding tools. Technology & Engineering Practices We believe strong engineering comes from good systems. Our teams focus on: Consistent architecture patterns across products. Automated testing. Code quality and review processes. Continuous improvement. Clear ownership. We use standards where they help, and we adapt when a problem genuinely requires something different. The Mainloop Barcelona Certificate We are building a structured engineering development program focused on: AI-native software development. Product ownership. Architecture. Building reliable applications. Taking software from idea to production. Engineers who complete the program and demonstrate mastery will receive the Mainloop Barcelona Certificate — a recognition of their ability to build modern software using AI-powered engineering methods. Relocation & Benefits For candidates relocating from North America, Mainloop provides: Visa sponsorship support. Relocation assistance. Initial accommodation support. Assistance with local administration. Spanish language support. Additional benefits include: Permanent full-time employment contract in Spain. Healthcare coverage from day one. 30 calendar days of annual vacation plus public holidays. Opportunity to work across international markets. Career growth within a global organization. The opportunity to help build a new AI-native engineering team. Why Barcelona? Barcelona offers: A strong international technology ecosystem. A vibrant engineering community. Excellent quality of life. Access to European markets. A multicultural environment. This is an opportunity to build your engineering career at the intersection of: Software Engineering + Artificial Intelligence + Product Ownership + Global Impact Hiring Process Our process is designed to understand how you think and build: Introductory conversation Learn about your background, experience, and what you are looking for. Engineering discussion Walk us through something you have built and discuss your technical decisions. Conversation with our global technology team Learn more about how we build and where we are going. Practical project Complete a real engineering exercise using the tools and workflow we use internally. Apply with something you have built and tell us about a technical decision you made, what you learned, and how you would approach it differently today. Mainloop | Barcelona, Spain Building the future of AI-native engineering.

What you’ll do

Requirements

Candidates should be able to build web applications across frontend and backend, understand software engineering fundamentals, improve existing codebases, and communicate clearly in English. Senior candidates should also have production ownership, architecture decision-making, and mentoring experience; junior candidates should demonstrate the ability to build a working application and motivation to grow with AI coding tools.