Senior Full-Stack Engineer, Autonomous Defense

Horizon3.ai

. Build and own the agent execution runtime with durable, resumable, long-running workflows, checkpointing, idempotent steps, cancellation, and timeouts .

Posted 11/3/2026full-timeRemote • United StatesSenior💰 $195,000 - $235,000 per yearWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in building and operating durable, multi-tenant systems with a focus on security and performance. Proficient in modern programming languages and frameworks, with a strong emphasis on backend API development and distributed systems.

Highest-signal resume keywords

Backend API DevelopmentReact And TypeScript ProficiencyExperience With AWS, Azure, Or GCPDistributed Systems DesignExpert Proficiency In SQL

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills

PythonGoScalaC++TypeScriptGraphQLSQLDockerKubernetesTemporal

Tools & Technologies

AWSAzureGCPDatadogPrometheusGrafanaWebSocketsReact QueryApolloPostgreSQL

Industry Keywords

Durable ExecutionMulti-Tenant PlatformsSecurity Control PlanesEDRSIEMCloud IAMAsynchronous WorkflowsCheckpointingAudit TrailsAgentic Systems

Tech Stack

Tools & technologies

ApolloAWSAzureCloudDistributed SystemsDockerETLFirewallsGoogle Cloud PlatformGrafanaGraphQLKubernetesNeo4jPostgresPrometheusPythonReactScalaSQLTypeScriptC++Go

About the role

Key responsibilities & impact

Build and own the agent execution runtime with durable, resumable, long-running workflows, checkpointing, idempotent steps, cancellation, and 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, firewall, 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
Build the operator-facing React and TypeScript front end
Build client-side data and streaming layers using WebSockets rather than polling
Extend tenant isolation for write-capable agents, including execution boundaries, egress control, quotas, and prevention of cross-tenant leakage
Develop ETL and GraphQL product features for data processing and retrieval
Build ETL pipelines that convert pentest and remediation outcomes into training and evaluation datasets
Instrument systems with distributed tracing, per-tenant cost and token accounting, and tooling to explain agent decisions
Partner with AI researchers, attack engineers, and product to move capabilities from prototype to production

Requirements

What you’ll need

Bachelor's Degree in Computer Science, Computer Engineering or related field
7+ years of professional software engineering experience using modern object-oriented or functional languages such as Python, Go, Scala, C++, or TypeScript
Proven experience delivering backend APIs, especially GraphQL, and consuming them from a modern web stack
Production experience with React, TypeScript, and modern CSS layout
Experience building applications on AWS, Azure, or GCP
Experience using 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 durable execution or workflow engines such as Temporal, or equivalent checkpointing experience
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 APIs, including EDR, firewalls, SIEM, and cloud IAM
Experience with PostgreSQL and Neo4j database architectures and GraphQL backends
Experience with React Query or Apollo, GraphQL subscriptions, and WebSockets
Experience building operator-facing or admin interfaces where density, auditability, and safe destructive actions matter
Experience with Datadog, Prometheus, Grafana, and distributed tracing
Awareness of prompt injection and untrusted-input handling
Willingness to travel up to 5%
Authorization to work in the United States is requested in the application form

Benefits

Comp & perks

Equity package in the form of stock options for all full-time roles
Health insurance for you and your family
Vision insurance for you and your family
Dental insurance for you and your family
Flexible vacation policy
Generous parental leave
Career development opportunities
Inclusive and collaborative work environment
Remote work