Senior Backend Engineer, Defensive Agent

🔥 14 hours ago

🇺🇸 United States – Remote

💵 $199k - $235k / year

⏰ Full Time

🟠 Senior

🔙 Backend Engineer

👻 Ghost score 20%

What it means: how likely this posting is sitting open without active hiring.How to read it: 60% or higher means we think this is a ghost. Lower scores are less of a worry.How we score it: age, reposts, open roles vs team size, how fast jobs close, and whether pay is listed.Fine print: an estimate from public data, not a judgment of the company. Real jobs can score high, so treat it as a hint, not a fact.

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Horizon3.ai

WebsiteLinkedInAll Job Openings

51 - 200 employees

Founded 2019

🔒 Cybersecurity

🤖 Artificial Intelligence

☁️ SaaS

Cybersecurity • Artificial Intelligence • SaaS

Horizon3. ai is a cybersecurity company that specializes in autonomous penetration testing through its platform, NodeZero. The company's mission is to proactively identify and address attack vectors before they can be exploited, allowing organizations to continuously assess their security posture across various environments including cloud, IoT, and on-premises systems. Founded by veterans from the US Special Operations and National Security sectors, Horizon3. ai offers a self-service SaaS solution that provides organizations with insights into their security vulnerabilities without requiring persistent or credentialed agents.

📋 Description

• Build and own the agent execution runtime with durable, resumable, long-running workflows, checkpointing, idempotent steps, cancellation, and step- and run-level timeouts • Design and implement the agent tool layer with registry versioning, schema validation, per-tenant enablement, and server-side authorization • Build the connector framework for third-party security control planes, including EDR, firewalls, identity, SIEM, and cloud IAM • Implement the safe-change pipeline with dry runs, simulation, blast-radius classification, approval gates, staged rollout, rollback, and immutable per-tenant audit trails • Extend tenant isolation for agents taking write actions, including execution boundaries, egress control, quotas, and prevention of cross-tenant leakage • Develop ETL and GraphQL product features for data processing and retrieval supporting agent context, run history, and remediation state • Build ETL pipelines that convert pentest and remediation outcomes into datasets for research training and evaluation • Instrument agent runs with distributed tracing, per-tenant cost and token accounting, and tooling to explain agent behavior • Partner with AI researchers, attack engineers, and product to move capabilities from prototype to production and feed platform constraints into research direction

🎯 Requirements

• Bachelor's Degree in Computer Science, Computer Engineering or related field • 7+ years professional software engineering experience using modern object-oriented or functional languages such as Python, Go, Scala, C++, or TypeScript • Experience building applications on cloud computing platforms such as AWS, Azure, or GCP • Experience with container technologies such as Docker and Kubernetes • Expert proficiency in SQL • Demonstrated experience designing and operating distributed systems in production, including asynchronous workflows, queues, retries, idempotency, and partial failure • Track record of shipping and operating production services, including on-call ownership • Experience building agentic or LLM-backed systems in production • Experience with a durable execution or workflow engine such as Temporal, or equivalent self-built checkpointing • Experience building multi-tenant platforms with hard isolation requirements, workload identity, and short-lived credential brokering • Experience integrating third-party APIs behind a normalized abstraction • Familiarity with security control planes and their APIs, including EDR, firewalls, SIEM, and cloud IAM • Experience with relational and graph database architectures, including PostgreSQL and Neo4j • Experience building GraphQL backends • Experience with observability tooling such as Datadog, Prometheus, and Grafana, and distributed tracing • Awareness of prompt injection and untrusted-input handling • Authorization to work in the United States is required by the application form

🏖️ Benefits

• Equity package in the form of stock options for all full-time roles • Health, vision & dental insurance for you and your family • Flexible vacation policy • Generous parental leave • Career development opportunities • Inclusive culture • Collaborative environment • Remote and hybrid work models depending on role and location