Senior Software Engineer (AI)

Location: Hybrid; position based in Spain

Salary: €111,000–€143,000 gross annual base wage for the position based in Spain.

Company

Justworks provides HR solutions that help businesses manage operations and focus on running their business.

What you will do

• Design, build, and own core components of an AI agent platform, including orchestration and internal tool integrations.
• Develop APIs, data access patterns, and service integrations that enable agents to execute operational workflows.
• Architect knowledge and memory infrastructure so agents can retrieve data and act across systems.
• Implement trust and safety capabilities, including audit trails, human-in-the-loop controls, and guardrails.
• Build agent evaluation and testing infrastructure to measure accuracy, reliability, and regressions.
• Partner with Operations to identify automation opportunities and mentor engineers as the team grows.

Requirements

• 5+ years of backend engineering experience building and operating production systems.
• Hands-on experience with LLMs and AI agents, including orchestration, RAG, or tool and function calling.
• Strong API design and system integration skills.
• Experience designing, building, and operating production systems with a strong ownership mindset.
• Product-minded approach and ability to make pragmatic decisions in ambiguous, early-stage environments.
• Experience or interest in technologies such as Golang, Ruby on Rails, JavaScript, Java, C#, Python, MySQL, Kafka, AWS, Redis, Docker, Terraform, Kubernetes, and CircleCI.

Culture & Benefits

• Welcoming, casual, and supportive work environment.
• Opportunity to work in a small, highly autonomous cross-functional team.
• Benefits and wellness program offerings.
• Company retreats and opportunities to learn from leaders in the startup community.
• Inclusive workplace focused on diversity, collaboration, and accessibility.