Antai Ventures is a Barcelona-based venture studio with presence across Southern Europe and Latam. At Antai, we partner up and invest in the best co‐founders to build global companies willing to disrupt multi‐billion dollar industries. We are looking for a Senior Full‐Stack Engineer to join the founding team of one of our portfolio companies — a B2B SaaS platform that helps service companies manage the complex, day‐to‐day operations of their distributed frontline workforce. The vision is ambitious: build the operating system for an entire industry — starting with day‐to‐day operations, then expanding into deeper integrations across finance, HR, and everything else these companies need to run their business. AI isn't a feature we'll bolt on — it's embedded from day one as a core capability that fundamentally changes how these companies operate.You'll be one of the first engineers on a small, high‐ownership team building a product from the ground up. This isn't a role where you'll be handed tickets — you'll be researching customer problems, crafting detailed specs, designing solutions, writing code, and shipping features end‐to‐end. You'll work directly with the founders and be expected to bring strong judgment about what to build, how to build it, and when to keep things simple.We need someone who is genuinely full‐stack: comfortable across backend, database, frontend, mobile (web‐based via Capacitor), and cloud infrastructure. Barcelona, hybrid (some office days)Full‐timeProficient English required. Spanish not required, but a basic level is a plus.Study customer problems deeply and translate insights into detailed functional and technical specs — then turn those specs into working software.Design and build core backend systems powering workforce scheduling, real‐time coordination, and operational workflows.Build clean, well‐structured APIs and data models that support web, mobile, and internal tools.Develop the worker‐facing mobile experience (web‐based, via Capacitor) with a focus on simplicity for low‐tech‐savviness users.Contribute to the AI agent's backend — the infrastructure that lets it resolve coverage incidents, contact workers, and take autonomous actions.Manage and evolve cloud infrastructure, CI/CD pipelines, and developer tooling.Improve reliability, observability, and performance across the system.Build integrations with other business software the industry already uses — accounting, payroll, and other operational tools.Participate in design reviews and product decisions, bringing engineering perspective to what gets built and how.Start crafting your own specs — studying a problem, collaborating with the team to refine the approach, designing the implementation, and seeing it through to production.Build and iterate on the worker‐facing mobile experience, making it intuitive for frontline workers with minimal tech experience.Get hands‐on with the local‐first sync layer (ElectricSQL, TanStack DB) as real usage reveals edge cases and design tradeoffs.Help shape the AI agent's capabilities — how it reasons about coverage, contacts workers, and escalates to managers.Improve the development workflow itself — testing patterns, CI/CD, tooling, and the feedback loop between specs and code.Throughout all of this, you'll be leveraging AI coding agents heavily — not as an afterthought, but as a core part of how you research, design, plan, implement, and review.Strong engineering fundamentalsYou're comfortable owning systems end‐to‐end: from research and spec writing, through design and implementation, to deployment and operations.You have solid experience with TypeScript, SQL, and modern web frameworks. Our stack is Vue, Nuxt 4, Nuxt UI, PostgreSQL, ZenStack/Prisma, ElectricSQL, TanStack DB, and Capacitor.You've worked with cloud infrastructure (GCP, AWS, or similar) and understand CI/CD, containerization, and production operations.AI‐augmented engineeringYou use AI coding agents daily and can orchestrate multi‐file agentic workflows with tools like Claude Code, Cursor, or similar — not just autocomplete, but steering complex architectural decisions and reviewing AI‐generated output for quality and maintainability.You can effectively amplify yourself using AI across the entire development lifecycle: research, spec writing, design, implementation, code review, and debugging.You deeply understand customers and their world, and you balance business goals and constraints in your engineering decisions.You anticipate problems before they arrive and know when to compromise, be pragmatic, and avoid over‐engineering.You thrive in the earliest stages of building — where there's no playbook, priorities shift fast, and the best move is often the scrappy one that gets things done now.You've been through the 0→1 phase before (or you're hungry for it) and you understand that speed of iteration matters more than perfection.Experience with local‐first / offline‐first architectures or real‐time sync.Experience building mobile apps with Capacitor or similar web‐to‐native bridges.You've worked in early‐stage startups and are comfortable with ambiguity and fast‐changing priorities.Spec‐driven development. Engineering decisions are informed and deliberate, not reactive.AI coding agents aren't a novelty here — they're part of how the team operates daily, across every phase of the development cycle.We use Linear for task‐centered work and value deliberate, organized communication. You'll shape the product and architecture from the earliest stage — the systems you build will exist for years.You'll have real ownership and direct impact on what gets built, how it's built, and how fast the company moves.You'll join a team that takes engineering craft seriously while staying pragmatic about what matters at this stage.You'll help define what "great engineering" looks like at a company that's just getting started.#