Senior Software Engineer (AI)

TL;DR

Senior Software Engineer (AI) (LLM agents/backend): Building an agent platform that reads operational knowledge, reasons in context, and executes HR workflows end-to-end with an accent on orchestration, integrations, knowledge infrastructure, and trust and safety. Focus on designing production-ready AI-native systems, evaluating agent reliability, and solving ambiguous technical challenges in an early-stage product environment.

Location: Hybrid role based in the United Kingdom

Salary: £132,000–£170,000 per year

Company

Justworks provides HR solutions that help businesses manage operational and people-related processes.

What you will do

• Design, build, and own core components of the 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 for data retrieval and cross-system actions.
• Implement trust and safety capabilities such as audit trails, human-in-the-loop controls, and guardrails.
• Build evaluation and testing infrastructure to measure agent accuracy, reliability, and regressions.
• Partner with Operations, 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, backend architecture, and system integration skills.
• Experience owning complex projects in ambiguous, early-stage environments.
• Product-minded approach with pragmatic decision-making, strong ownership, and a focus on production quality.
• Ability to work in a hybrid setup based in the United Kingdom.

Nice to have

• Experience with Golang, Ruby on Rails, Java, C#, Python, Vue, MySQL, Kafka, AWS, Redis, Elasticsearch, Docker, Terraform, Kubernetes, CircleCI, or Datadog.
• Experience mentoring engineers or contributing to product decisions.

Culture & Benefits

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