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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Senior Fullstack Engineer - **Company:** Moonfire - **Location:** Barcelona, Spain (Remote available) - **Contract:** Permanent contract - **Skills:** Application Programming Interfaces (APIs), User Authentication, Software Bug Management, Databases, Data Structures, Programming Tools, Github, PostgreSQL, Routing, Node.Js, Open Source Technology, Systems Integration, TypeScript, Encapsulation (Networking), Web Applications, Network Routers, ReactJS, Express.js, AI Coding Agents, Backend, Agentic-AI, Webpack, Material UI, Information Technology, Cloudflare, Virtual Agents, Api Design, Web Api - **Published:** November 5, 2026 - **Apply:** https://www.buscojobs.com.es/senior-fullstack-engineer-en-barcelona-ID-378770698 ## About the Role Built an own app, or side project that others have used - could be a tool for a friend, a small product, an open-source package, anything real people relied on 5+ years of production experience with TypeScript and Node.js Expert React knowledge - Suspense-first patterns, skeleton loaders, loading states Experience with SSR, CSR, and SSG Deep expertise with React routing libraries Built or contributed to design systems / component libraries used by others Experience designing navigation, onboarding flows, and user journeys Backend experience with Node.js (Express.js or similar) and PostgreSQL Experience designing production-ready APIs Experience with authentication and authorization systems CS degree or equivalent - algorithms, data structures, system design Prior remote work experience in distributed teams Available 7-10am San Francisco time daily Fluent English Deep knowledge of AI coding tools and workflows - you use them daily and know how to get the most out of them Optional Skills Experience with Cloudflare platform (Workers, etc.) Experience with Row-Level Security (RLS) in Supabase/PostgreSQL Experience with background job workflows Built an AI agent before Contributed to a design system or React component library used by other teams Experience with observability and monitoring Open source contributions Speaking multiple languages is a plus You love Remix, React Router, TanStack Router, or TanStack Start ## Description About the Project & TeamWe started Lingo.dev at a hackathon and, after winning the best dev tool award, we just kept building. It evolved into a developer-loved toolkit with hundreds of active users, 7,000 weekly CLI runs, 5,000 GitHub stars, and over 100 million translated words. We've graduated from the world's best tech accelerator (Y Combinator) and raised venture funding to continue building developer tools that must exist but don't yet.We're a small, fully remote team of senior engineers who like to work hard on interesting problems. We value computer science craft over corporate politics and love building tools for developers - including ourselves. Recently we started getting more feature requests than we can ship, so we're excited to expand the team.Job FunctionsAs part of a team of senior engineers, design, develop, and grow the Lingo.dev productsWeb applications - Routing, navigation, onboarding flows, user experience, performanceOpen source tools - CLI, webpack/vite pluginsBackend APIs - encapsulation, API design, securityDatabase layer (PostgreSQL)Integrations - with 3rd party systemsAI agentsTake full ownership of features from design to deployment: draft technical designs, review with founders + the team, implement end-to-end with tests and documentation3 sprints of product roadmap work, 1 cooldown sprint (customer feature requests, improvements, bug fixes)Weekly Demo Days with the rest of the teamRequirementsBuilt an own app, or side project that others have used - could be a tool for a friend, a small product, an open-source package, anything real people relied on5+ years of production experience with TypeScript and Node.jsExpert React knowledge - Suspense-first patterns, skeleton loaders, loading statesExperience with SSR, CSR, and SSGDeep expertise with React routing librariesBuilt or contributed to design systems / component libraries used by othersExperience designing navigation, onboarding flows, and user journeysBackend experience with Node.js (Express.js or similar) and PostgreSQLExperience designing production-ready APIsExperience with authentication and authorization systemsCS degree or equivalent - algorithms, data structures, system designPrior remote work experience in distributed teamsAvailable 7-10am San Francisco time dailyFluent EnglishDeep knowledge of AI coding tools and workflows - you use them daily and know how to get the most out of themOptional SkillsExperience with Cloudflare platform (Workers, etc.)Experience with Row-Level Security (RLS) in Supabase/PostgreSQLExperience with background job workflowsBuilt an AI agent beforeContributed to a design system or React component library used by other teamsExperience with observability and monitoringOpen source contributionsSpeaking multiple languages is a plusYou love Remix, React Router, TanStack Router, or TanStack StartBenefitsOpportunity to work with latest, cutting-edge technologiesWork directly with users using what you build every daySmall team working directly with foundersBe a part of open-source communityOccasional travel to meet the team in personConference and learning budgetFlexible working hoursCompetitive salaryHealth insuranceInterview ProcessScreening Call (Technical/Cultural Fit)Live Coding / Technical Project: Evaluating CS fundamentals and architectural depth (algorithms, system design)Final Deep Dive (System Design & Partnership)After passing the interviews, there's a one-month paid trial period. It's intense - we'll work closely together on real features to make sure we work well together.Do Not Apply IfYou are looking for passive, hands-off remote work with minimal team interactionUncertainty makes you uncomfortable - you prefer detailed specs over figuring things out as you goYou are unwilling to prioritize customer needs over your preferred patterns or tools#J-*****-Ljbffr