Senior AI Platform Engineer (LLM & Agents)

Justworks; United States; Remote; USD 150,000 - 210,000; Full time

Job summary

Justworks is seeking a Senior Software Engineer to join a small, autonomous team building AI-native systems for operations at scale. You will own large segments of the tech stack, make pragmatic decisions in emerging territory, and ship production-ready systems that power real customer workflows.

You will contribute to the agent platform, design robust backend services, and drive knowledge infrastructure while collaborating with operations to automate complex processes.

Qualifications

• 5+ years of backend engineering experience
• Hands-on experience with LLMs and AI agents (orchestration, RAG, tool/function calling)
• Strong API design and system integration skills
• Product-minded: contribute 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 engineering

LLMs & AI agents

API design

Product-minded

Ownership

Job description

Justworks is seeking a Senior Software Engineer to join a small, autonomous team building AI-native systems for operations at scale. You will own large segments of the tech stack, make pragmatic decisions in emerging territory, and ship production-ready systems that power real customer workflows.

You will contribute to the agent platform, design robust backend services, and drive knowledge infrastructure while collaborating with operations to automate complex processes.