Senior Backend Engineer, External

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. 

What You’ll Do

As a Senior Backend Engineer on the External Attack team, you'll contribute to the full set of backend services that power NodeZero's external pentesting capabilities, from architecture and development through deployment and production operations. You'll own parts of our core API, data processing and ETL pipelines, datalake, graph, along with the container orchestration and cloud infrastructure beneath it all. You'll be accountable for the performance, scalability, and uptime of several of these services, and you'll be a key contributor to user-facing product launches and platform stability.

Responsibilities

• Design, build, and maintain features in our core Python API, with a focus on performance, correctness, and maintainability.

• Design, build, and operate workflow orchestration for large-scale, long-running workloads using tools such as Prefect or Temporal, including scheduling, retries, idempotency, state management, and failure recovery.

• Build orchestration that scales reliably across many concurrent workflows, with clear visibility into progress, failures, and throughput.

• Comfort reading and untangling unfamiliar, complex SQL, and the judgment to optimize or refactor it safely in production.

• Build and operate high-throughput data processing and ETL pipelines that turn large volumes of raw assessment data into reliable, queryable datasets.

• Contribute to datalake architecture on AWS, including storage layout, partitioning, schema evolution, and query performance.

• Deploy and manage services on Kubernetes, and take part in cluster operations, release management, and capacity planning.

• Develop and extend GraphQL and graph-based APIs that let product components and customers explore complex relationships in their data.

• Own the observability, uptime, and scalability of the services you build, including metrics, tracing, alerting, and on-call participation.

• Partner with frontend engineers, product managers, and designers to turn backend capabilities into a clear, responsive user experience.

• Contribute to systems architecture decisions and write design docs that help the team move quickly with shared understanding.

• Collaborate with frontend team members to present data in a clear and user-friendly format, enhancing the product's user experience.

What You’ll Bring

• The ability to own and manage concurrent initiatives, with sound judgment in prioritization and time management.

• A self-driven approach: you can conceive and implement solutions on your own and with a team.

• A reliability mindset for distributed work: you design for retries, partial failure, and recovery, and you debug asynchronous systems methodically.

• A strong desire to keep learning new technologies in a fast-paced Agile environment.

• Excellent analytical and problem-solving skills, clear communication, and attention to detail.

• A bias toward operational ownership: you care how your code behaves in production

• Strong technical writing for design docs, runbooks, and API documentation.

• Effective collaboration with designers, developers, and product managers.

Required Education / Experience

• Bachelor's Degree in Computer Science, Computer Engineering or related field.

• 7+ yrs professional software engineering experience using modern object-oriented or functional languages (Python, Java, Go, Scala, C++, TypeScript, etc).

• Experience building and running workflow orchestration or distributed task-processing systems in production (for example Prefect, Temporal, Airflow, Celery, or similar).

• Hands-on experience designing and building high-throughput data processing systems and ETL pipelines.

• Experience building applications on cloud computing platforms such as AWS, Azure, GCP, using container technologies such as Docker and Kubernetes.

What Sets You Apart

• Deep Kubernetes experience, including managing deployments and clusters and troubleshooting production workloads.

• Experience with durable-execution or workflow engines such as Temporal or Prefect, including designing workflows that are resilient, observable, and easy to evolve.

• Experience building GraphQL backends and working with graph databases

• A track record of owning observability, uptime, and scalability for production systems (for example Datadog, Prometheus, or OpenTelemetry).

• Systems engineering and architecture experience with datalakes and the cloud services around them.

• Experience building platform capabilities or internal tooling that other engineering teams rely on.

• Experience in cybersecurity or with attack surface and vulnerability data.

Only US persons can interview for this role due to security clearance requirements by our customer(s) and/or vendor(s). Employee must be eligible for and successfully secure a US Federal Security Clearance as a condition of employment.

Travel Required

We are a fully remote company, and this job may require up to 5% of travel to be successful.

Perks of Horizon3

• Inclusive Team: We value diversity and promote an inclusive culture where everyone can thrive.

• Hybrid & Remote Work: We embrace a mix of remote and hybrid work models depending on role and location, including our Chicago office, where some roles require regular in-office presence.

• Base salary range: $199,750 - $235,000 annually. The exact salary will be determined based on the selected candidate’s location, qualifications, experience, and relevant skills.

You Belong Here

Horizon3 is not just an equal opportunity employer - we are a community that values diversity, equity, and inclusion as fundamental principles of our culture and success. We are dedicated to fostering a workplace where everyone feels welcome and respected, regardless of race, color, religion, sex, national origin, age, disability, veteran status, sexual orientation, gender identity or expression, genetic information, marital status, or any other legally protected status by law.