Senior AI Software Engineer – Applied AI Platform (Remote UK)

Justworks, Inc.; United Kingdom; Remote; GBP 132,000 - 170,000; Full time

Job summary

Justworks, Inc. in the United Kingdom is seeking a Senior Software Engineer, Applied AI to join a small, autonomous team building an AI-native agent platform that can read operational knowledge, reason about it in context, and execute tasks end-to-end.

This is a highly collaborative role focused on delivering scalable, robust AI-driven services. You will work on designing, implementing, and scaling production systems, with emphasis on safe, trusted AI operations and strong API/data layer

Qualifications

• 5+ years of backend engineering experience building and operating production systems.
• Hands-on experience with LLMs and AI agents (orchestration, RAG, tool/function calling, or similar)
• Strong API design and system integration skills
• Product-minded: questions requirements and contributes to product decisions, not just execution
• Proven ownership of complex projects in ambiguous, early-stage environments

Responsibilities

• Design, build, and own core components of the agent platform, from the orchestration layer to the tool integrations connecting it to internal systems.
• Build and evolve the capabilities layer: APIs, data access patterns, and service integrations for agents to execute operational workflows.
• Architect the knowledge and memory infrastructure, allowing agents to retrieve the data and act across our systems.
• Design and implement the trust and safety framework, including audit trails, human-in-the-loop controls, and guardrails for safe and auditable AI-driven operations.
• Contribute to agent evaluation and testing infrastructure, defining how we measure accuracy, reliability, and regression across agent behaviors.
• Partner directly with Operations to understand workflows, identify automation opportunities, and translate process knowledge into agent capabilities.
• Mentor other engineers on the team as it grows.

Skills

Backend experience

LLMs & AI agents

API design

Product-minded

Ownership

Job description

Justworks, Inc. in the United Kingdom is seeking a Senior Software Engineer, Applied AI to join a small, autonomous team building an AI-native agent platform that can read operational knowledge, reason about it in context, and execute tasks end-to-end.

This is a highly collaborative role focused on delivering scalable, robust AI-driven services. You will work on designing, implementing, and scaling production systems, with emphasis on safe, trusted AI operations and strong API/data layer