Senior AI-Native Backend Engineer

Justworks; United States; Remote; USD 140,000 - 190,000; Full time

Job summary

Justworks is seeking a Senior Software Engineer to join a small, autonomous team building an AI-native agent platform that reads knowledge, reasons in context, and executes tasks end-to-end. You will own large segments of the stack, craft robust backend systems, and collaborate with operations to translate workflows into scalable automation.

You will ship production-ready solutions and mentor growing engineers in a fast-paced startup environment, contributing to the evolution of our agent

Qualifications

• 5+ years of backend engineering experience.
• 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 orchestration to tool integrations.
• 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 for data retrieval across systems.
• Design and implement trust and safety framework with audit trails and human-in-the-loop controls.
• Contribute to agent evaluation and testing infrastructure for accuracy and reliability.
• Collaborate with Operations to translate workflows into agent capabilities.
• Mentor other engineers on the team as it grows.

Skills

Backend engineering

LLMs

AI agents

API design

System integration

Product mindset

Project ownership

Job description

Justworks is seeking a Senior Software Engineer to join a small, autonomous team building an AI-native agent platform that reads knowledge, reasons in context, and executes tasks end-to-end. You will own large segments of the stack, craft robust backend systems, and collaborate with operations to translate workflows into scalable automation.

You will ship production-ready solutions and mentor growing engineers in a fast-paced startup environment, contributing to the evolution of our agent