Senior Software Engineer - Fountain One
Software Engineering
Madrid, Spain
Posted on May 30, 2026
Fountain builds workforce management software for the world's largest hourly employers. We are an agent-first engineering organization where coding and review agents are integrated into our daily workflow. Our platform team builds the critical systems that enable engineers and agents to ship dependable products at scale. What You’ll be Doing:- Ship platform capabilities across all customer and internal products- Own performance, security, and stability for high-traffic production systems- Enhance agentic systems, including coding agents and observability tools- Lead architectural decisions for human and agentic interfaces- Design reliable code, APIs, and contracts for humans and agents- Collaborate with product and engineering teams to deliver customer impact- Work autonomously with product managers and designers- Identify problems, ship fixes, and own outcomes like an early-stage product team What you bring:- 5+ years backend-focused engineering; shipped production-ready systems- Expert systems design and technical leadership- Strong judgment for trade-offs, UX, APIs, and code standards- Experience with agentic/LLM-based systems in production; designed evals catching regressions- Initiative; thrives in autonomy/ambiguity; excellent written communication Nice to have:- Designed APIs/tools for agents; early-stage/startup experience; event-driven architectures/monorepos/observability