Full-Stack Engineer - Mainloop - Barcelona, Spain

Overview

In this AI-native role, you own production software across a varied product portfolio built for professional services. You join a new Barcelona team that handles architecture, quality, and releases, while collaborating with a Product Owner to shape the product you ship. You work with AI agents to accelerate development and maintain production-grade systems.

The role emphasizes ownership, architectural judgment, and moving from prototype to dependable software that scales across countries.

• Own a product end-to-end: architecture, quality, and releases
• Keep products evolving to maintain adoption and value
• Design with a focus on architecture and business impact
• Start and own new products as they arrive
• Collaborate with PO to translate needs into precise specifications
• Review merges via agent-assisted processes and ensure 100% test pass
• Define and implement robust AI-powered testing and evals
• Own production incidents during working hours and drive fixes
• Contribute to standard, scalable engineering practices across projects
• Shape team processes and contribute to the architecture over time

• Ownership of production software experience
• Full-stack capability across front and back of web apps
• Strong TypeScript proficiency; other languages acceptable
• Experience with testing: unit, end-to-end, and smoke tests
• Comfort using coding agents and reading their outputs
• Ability to understand and explain unfamiliar codebases
• Fluent English; Spanish useful; Barcelona location
• Willingness to work with AI agents and build with them
• Ability to reason about architecture and long-term code health
• Problem-solving mindset and stake in product quality

• Judgment and decisiveness
• Ability to disagree constructively with stakeholders
• Mentoring teammates
• TypeScript
• AI agents (Claude Code, Claude Max, Cursor or Codex)
• Playwright end-to-end testing