Senior Backend Engineer — Remote Defensive AI Platform

horizon3ai; United States; Hybrid; USD 170,000 - 235,000; Full time

Benefits offered by this job

Inclusive Team

Growth Opportunities

Innovative Culture

Hybrid & Remote Work

Competitive Compensation

Job summary

Horizon3 is a fast-growing, remote cybersecurity company delivering NodeZero, a platform that runs autonomous pentests across diverse environments. As a Senior Backend Engineer on the Defensive Agent team, you’ll build the platform that the defensive agents run on, enabling production-safe automation and scalable security assessments.

You’ll own runtime, tool layers, orchestration, connectors, and observability.

Qualifications

• Bachelor's degree in CS, CE, or related field.
• 7+ years of professional software engineering experience.
• Experience with cloud platforms (AWS, Azure, GCP) and container tech (Docker, Kubernetes).
• Expert proficiency in SQL.
• Experience designing and operating distributed systems in production: asynchronous workflows, queues, retries, idempotency.
• Track record of shipping and operating production services, including on-call ownership.

Responsibilities

• Build and own the agent execution runtime with durable, long-running workflows.
• Design the tool layer used by agents, with per-tenant enablement and server-side auth.
• Create the connector framework for third-party security controls (EDR, firewall, IAM, SIEM).
• Implement the safe-change pipeline: dry-run, simulations, approval gates, rollout, rollback, and immutable audit trails.
• Extend multi-tenant isolation for agents, including egress control and quotas.
• Develop core ETL and GraphQL features for data processing and retrieval of agent context and remediation state.
• Build ETL pipelines turning pentest outcomes into datasets for researchers.
• Instrument systems with distributed tracing, cost accounting, and diagnostics.

Skills

Distributed systems

Backend engineering

Python

Go

Scala

C++

TypeScript

SQL

Education

Bachelor's degree in CS/Engineering

Tools

AWS

Azure

GCP

Docker

Kubernetes

Temporal

PostgreSQL

Neo4j

Job description

Horizon3 is a fast-growing, remote cybersecurity company delivering NodeZero, a platform that runs autonomous pentests across diverse environments. As a Senior Backend Engineer on the Defensive Agent team, you’ll build the platform that the defensive agents run on, enabling production-safe automation and scalable security assessments.

You’ll own runtime, tool layers, orchestration, connectors, and observability.