Senior Backend Engineer, Integrations

Get to Know Us Horizon3 is a fast-growing, remote cybersecurity company dedicated to the mission of enabling organizations to proactively find and fix and verify exploitable attack vectors before criminals exploit them. Our flagship product, the NodeZeroTM platform, delivers production-safe autonomous pentests and other key assessment operations that scale across the largest internal, external, cloud, and hybrid cloud environments. NodeZero has been adopted by organizations of all sizes, from small educational institutions to government agencies and Global 100 enterprises. It is used by ITOps/SecOps teams, consulting pentesters, and MSSPs and MSPs.  We are a fusion of former U.S. Special Operations cyber operators, startup engineers, and formerly frustrated cybersecurity practitioners. We're committed to helping solve our common security problems: ineffective security tools, false positives resulting in alert fatigue, blind spots, "checkbox” security culture, cybersecurity skills shortage, and the long lead time and expense of hiring outside consultants. Collectively, we are a team of learn it alls, committed to a culture of respect, collaboration, ownership, and results.   WHAT YOU'LL DO You'll be joining the Platform Integration Team (PIT Crew) — a high-impact group whose mandate is critical to the scalability and extensibility of the NodeZero platform. The PIT Crew's mission is to transform Horizon3's APIs and integrations from a collection of one-off vendor connectors into a consistent, documented, permission-aware platform. You'll build the systems that let customers connect NodeZero to the tools they already rely on across the security and IT ecosystem. This is a senior individual contributor role. You'll lead through technical judgment, cross-functional partnership, and high-quality execution — owning significant pieces of platform infrastructure while helping set the standard for the team. In this role, you will: - API Platform: evolving our internal GraphQL-federated API into a first-class, customer-facing product — with permissions, multi-account scoping, versioning, schema evolution, and documentation. - Integration Platform: building and operating a shared Integration Router so new connectors can be configured and declared rather than built from scratch, with reusable authentication, health checks, and workflow execution. - Security-Tool Integrations: shipping and maintaining integrations with the tools customers already use — CrowdStrike, Splunk, ServiceNow, Jira, Palo Alto, SentinelOne, and others in the SIEM, EDR, and ticketing ecosystem. - MCP Platform: expanding our customer-facing MCP server and agentic workflow capabilities across US, EU, and Australia production environments, enabling customers to build their own AI-powered workflows atop NodeZero data. - You'll also share on-call responsibility for a substantial production-observability footprint (Datadog, Kafka-triggered services, multiple environments), meaning you're not just shipping integrations — you're operating them. What You'll Be Responsible For - Design and implement backend APIs in GraphQL — including federated subgraph development, schema evolution, and multi-account query scoping for MSSP and multi-subsidiary customers. - Build and extend the Integration Router: connector libraries, workflow configuration, secrets management, vendor adapters, and Kafka-triggered dispatch services. - Own production reliability for API and integration services: monitoring, alerting, deployment, vendor API drift, rate limits, retries, and safe failure handling. - Contribute to the MCP platform and OAuth proxy layer, including tool authentication and agentic workflow support. - Contribute production code that sets the standard for desig