Barcelona, Spain — hybridFull-time employment0.5–1% equity
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About Our Client
Our client is an early-stage technology company building an AI-native platform for complex hardware engineering.
The platform brings system architecture, requirements, verification, engineering workflows, and technical decisions into one traceable environment. It provides engineers and AI agents with the context required to design, validate, and evolve complex hardware systems more effectively.
The technology can be applied across aerospace, defence, robotics, transportation, semiconductors, and other advanced engineering industries.
The product is already live and used by customers. The company is now preparing for its next stage of growth, including a planned seed funding round in autumn 2026.
The team currently consists of two founders supported by an external engineering team. This hire will become the first senior technical leader brought fully in-house.
About the Role
Our client is looking for a deeply hands-on software architect who can become the technical reference point for the product and the future engineering team.
You will work directly with the founders, take ownership of the existing architecture and production environment, and gradually assume responsibility currently held by an external software architect.
This is not an enterprise architect or people-management position. You will spend most of your time designing, building, reviewing, debugging, and shipping production software.
You will also own the decisions behind the implementation: how services and data models should be designed,



which technologies are appropriate, where strong foundations are necessary, and where a simpler solution is better.
As the company grows, you will help hire the first internal engineers, establish the engineering culture, and have the opportunity to develop into a broader technical leadership role.
What You Will Do
Take technical ownership of the existing product and production environment
Design and evolve the backend architecture, APIs, and relational data model
Build product capabilities across backend, frontend, infrastructure, and AI systems
Review code in depth and maintain ownership of technical quality, including AI-generated code
Define practical standards for architecture, testing, security, observability, releases, and documentation
Improve development speed without creating unnecessary complexity or operational fragility
Work directly with founders and customers to turn ambiguous needs into product and technical decisions
Explain technical alternatives, trade-offs, risks, and failure modes clearly
Support the transition from an external development team to an internal engineering organization
Help assess, hire, mentor, and set the technical bar for future engineers
What We’re Looking For
6–10 years of professional software engineering experience
Strong hands-on experience owning production software systems




Particular depth in backend architecture and relational database design
Strong TypeScript experience, ideally across both backend and frontend
Experience designing APIs, services, modules, integrations, and clear system boundaries
Strong knowledge of PostgreSQL or another relational database, including data modelling, performance, migrations, integrity, and access control
Experience with React, Next.js, or another modern frontend framework
Practical experience with Docker, cloud deployment, CI/CD, xqbhyrx monitoring, and production debugging
Evidence of taking ambiguous product problems from initial requirements through production and ongoing operation
Experience making technical decisions and explaining the alternatives and trade-offs behind them
A production mindset covering security, testing, observability, reliability, performance, and maintainability
Experience working in an early-stage startup, scale‑up, or similarly high‑ownership environment
Clear and concise technical communication in English
Based in Barcelona or genuinely willing to relocate
The right to work in the EU without visa sponsorship
The Person Who Will Succeed in This Role
want to build rather than manage from a distance;
are comfortable working without a detailed roadmap or established engineering organization;
investigate systems methodically instead of replacing components you do not immediately understand;
have strong opinions but can change them when the evidence changes;
can challenge founders constructively and explain the business impact of technical decisions;
communicate risks early and bring possible solutions; …
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📌 Founding Software Architect (Barcelona)
🏢 OnHires
📍 Barcelona