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Job · Medior

Full Stack Engineer, AI Systems

Fullstack Developer • Medior • Remote • Full-time • Spain Spain

ActAI is looking for a Full Stack Engineer for AI systems to build the product layer that turns AI capabilities into usable, production-grade workflows, including designing how agents operate, fail, recover, and deliver value.

Responsibilities

  • ▹Build end-to-end product features across frontend, backend, and AI integrations
  • ▹Design agent workflows that handle planning, tool use, failure, and recovery across multiple steps
  • ▹Integrate LLMs, memory, and external tools into systems that behave reliably under real-world conditions
  • ▹Design real-time AI interactions with streaming, partial results, and tight latency constraints
  • ▹Improve system reliability, observability, and fallback mechanisms
  • ▹Collaborate closely with ML, backend, and product teams to ship features end-to-end
  • ▹Continuously iterate based on real usage and failure modes

Requirements

  • ▹Strong experience in full stack engineering (frontend + backend)
  • ▹Solid understanding of system design and API architecture
  • ▹Experience working with LLMs, RAG systems, or AI-powered applications
  • ▹Ability to handle ambiguity and make pragmatic engineering decisions
  • ▹Strong ownership, able to take features from idea to production
  • ▹Comfort working in fast-moving environments with evolving requirements
  • ▹Tech stack: Next.js, Python, Node.js, PyTorch, OpenAI/Anthropic and open-source LLMs, SQL & NoSQL, Kubernetes, Docker

Soft skills

Strong ownership and independencePragmatic decision-making under ambiguity

About the company

ActAI builds proactive, AI-native applications for people who aren't used to complex prompting, aiming to bring intelligence into conversations, errands, and workflows with minimal prompting, focused on reliable long-running task completion and persistent context.

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