Full Stack Engineer

maintain modern, scalable web applications using Node.js / Bun, React, and Next.js. Collaborate closely with clients and teammates in a friendly, remote-first environment. Contribute to architecture decisions and ensure maintainable, well-documented codebases. Design and implement agentic workflows using AI coding agents, including multi-agent architectures for tasks such as testing, refactoring, and code review. Define prompting strategies and context management patterns that make AI-assisted development reliable and repeatable across the team. Help us evolve our internal tools, workflows, and development culture around AI-augmented engineering. General Skills Excellent communication with clients and teammates. Strong writing, communication, and documentation skills. Strong self-management skills for remote work. High attention to detail. Positive attitude towards new challenges and a fast learner. Proactive and able to work independently on self-managed projects. Experience working

with AI agents, sub-agents, and agent orchestration as part of daily development workflows. Fluent in written and spoken Spanish. Fluent in written and spoken English. AI Skills Hands-on experience developing with AI coding agents (Claude Code, Cursor, Codex, or similar) as a core part of your workflow. Deep understanding of how coding agents work: tokenization, context windows, sub agents, tools and skills. Experience working with Spec Driven AI Development and/or Research Plan Implement (RPI) methodologies. Experience designing agentic and multi-agent workflows, orchestrating sub-agents, chaining outputs, and managing context across agent interactions. Familiarity with AI orchestration tools and frameworks (n8n, LangChain, LangGraph, CrewAI, or similar) is a plus. Technical Skills Knowledge of software architectural principles such as Clean Architecture, DDD (Domain Driven Design), and Hexagonal Architecture. 5+ years of production experience with modern web stacks. We primarily work with Node.js / Bun, React, and Next.js (App Router, Server Components). Solid understanding of relational databases, SQL, and data modelling. Knowledge of Tailwind CSS for styling. Experience with Docker and containerized environments in development and production. Familiar with testing strategies and frameworks such as Jest or Cypress. Ability to build software that's scalable, maintainable, and well-documented. Location This position is only open to applicants residing in Europe who hold a valid work permit authorizing employment in the region. Why MarsBased? We're a boutique agency, not a factory. We work with clients who respect our time, process, and standards. You'll be part of a senior team where your voice matters and your work has real impact. The way software gets built is changing fundamentally. We're not waiting around, we're actively reshaping how we work with AI at every level. If you want to be at the front of that shift inside a team that's genuinely pushing innovation, this is the place. Join us and help us build software that lasts, from Mars, or anywhere you call home.

MarsBased is a development agency from Barcelona specializing in AI-augmented software development. We build end-to-end web & mobile apps using AI agents, agentic workflows, and modern engineering methodologies, delivering higher quality software, faster. We believe in remote work, scalable and maintainable solutions, and pushing the boundaries of what's possible when AI and human expertise work together. We're looking for a Senior Full Stack Engineer who doesn't just use AI tools, but thinks in AI-native workflows. Someone with a deep understanding of the entire software development lifecycle: from frameworks and programming languages to DevOps, infrastructure, performance, security, and monitoring. We need engineers who can leverage AI precisely because they understand what good software looks like end to end. You'll be joining a small, senior, and highly-collaborative team that values autonomy, quality, and transparency. We build things the right way. What you'll do Build and