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Salary: USD 148,750 - 190,000 / annual
Horizon3.ai is a fast-growing remote cybersecurity company building NodeZero, an autonomous penetration testing platform that helps organizations proactively identify and fix exploitable attack vectors. The company is founded by former U.S. Special Operations cyber operators and startup engineers, serving organizations from educational institutions to Global 100 enterprises.
The Software Engineer on the API Platform team will build and maintain the internal API layer that connects NodeZero's services and powers customer-facing interfaces and integrations. The API Platform team owns the gateway, API contracts, and shared platform capabilities consumed by other engineering teams. Your work directly impacts the reliability, latency, and developer experience of NodeZero's service mesh.
You'll join a small, focused team led by a P5 technical lead and P4 senior engineer, shipping against a roadmap that includes API consolidation, versioning, rate limiting, and observability improvements. The role reports to the API Platform Engineering Manager.
Key responsibilities include:
- Implementing and maintaining API endpoints, middleware, and platform services in Go
- Building and evolving the API gateway layer (routing, authentication, rate limiting, request/response shaping)
- Writing and maintaining API contracts (OpenAPI/gRPC definitions) and communicating breaking changes to internal consumers
- Contributing to service reliability through monitoring, alerting, SLA tracking, and incident response
- Writing clear, testable code covering both happy paths and failure modes
- Collaborating with Data Ingestion, Integrations Platform, and Client Platform teams
The company is fully remote with up to 5% travel required. Horizon3 emphasizes a culture of respect, collaboration, ownership, and results, with competitive compensation including equity packages, comprehensive health benefits, flexible vacation, and generous parental leave.
REQUIREMENTS:
- 2+ years of professional software engineering experience building production backend services
- Proficiency in Go or strong motivation to ramp quickly (Go is the primary language)
- Solid understanding of REST API design principles and HTTP semantics
- Ability to reason about service reliability (latency, error rates, retry behavior, circuit breaking)
- Comfort working in Kubernetes-based environments (deploying, debugging, service interaction)
- Experience with containerized development workflows (Docker)
- Familiarity with API authentication patterns (OAuth 2.0, API keys, JWT)
- Clear code writing with good naming, small functions, and meaningful tests
- Ability to communicate blockers early and work asynchronously across distributed teams
NICE TO HAVES:
- Experience with API gateway technologies (Kong, Envoy, NGINX, cloud-native equivalents)
- Exposure to service mesh architectures (Istio, Linkerd)
- Background in cybersecurity or experience building APIs for security tools
- Experience with gRPC and protobuf-defined service contracts
