Senior Software Engineer - Networking

The weaponization of AI is driving a paradigm shift in the cyber security industry from proactive to preemptive security: clients must now invest more intelligence and effort in understanding their vulnerabilities before their adversaries do (Open AI). The only way to achieve this is to simulate future attack scenarios at scale, and to run them in high fidelity digital replicas of production environments (Gartner/Forrester). SimSpace serves as the AI Proving Grounds to generate hypersynthetic data which pressure tests controls, tools, teams, and agentic capabilities in full kill chain attacks hidden in realistic environmental traffic and patterns of life.

Founded in 2015 by experts from U.S. Cyber Command and MIT Lincoln Laboratory, the platform was initially conceived to assist in Offensive Cyber Operations (OCO), to quickly replicate target environments to conduct mission rehearsal of human operators and their tools to deny (disrupt, degrade, destroy) or deceive (manipulate or exfiltrate data) adversaries. The company has since expanded to serve over a dozen allied governments in OCO/DCO as well as critical infrastructure enterprises around the world. The company is actively investing in the Americas, Asia Pacific, Europe and the Middle East through direct sales and channel partners. SimSpace has launched the AI Proving Grounds Consortium, leading the revolution by creating an open platform for the InfoSec ecosystem to train, validate and operationalize their agentic capabilities before committing to production.

Why join SimSpace?

We are a team united by a shared purpose and four core values: Serve to Protect, Acquire Understanding, Teamwork without Borders, and Operate as Innovators. We value candid, constructive feedback and create opportunities for personal, professional, and financial growth. Our vision, “Defend the Free World,” drives our mission: “Defeat Any Adversary in Any Cyber Terrain at Machine Speed.”

How Do We Work?

We listen to customers and colleagues, challenge assumptions, and turn ideas into meaningful results. We expect everyone to embrace emerging technologies, simplify and automate work, and use AI to learn, solve problems, and help deliver quality with speed. We apply human judgment and take responsibility for outcomes. Whether remote or office-based, we collaborate across teams and time zones.

We invite you to apply today!

We are looking for a Senior Software Engineer, Greyspace, to design and develop a realistic, simulated internet for SimSpace cyber ranges. You will help build the services, networking, and operator workflows that make training environments believable, repeatable, and safely contained. The ideal candidate brings deep experience building distributed software systems, strong networking fundamentals, and the ability to turn ambiguous requirements into working software across team boundaries.

In this hands-on engineering role, you'll contribute to Greyspace's architecture and implementation with Product, Security, and engineering partners. You will write and review code, prove architectural decisions through working increments, and take services from early implementations to reliable operation. The focus is on building reusable simulated services with clear isolation boundaries and integrating them into the SimSpace platform. Specifically, this position will be responsible for:

• Greyspace service architecture, APIs, and orchestration for configuring and managing simulated internet environments
• Realistic network and application behavior, including DNS, TLS, web, and mail services
• Reusable services and content with isolated per-range configuration, identities, and mutable state
• Platform and range integrations, operator workflows, automated validation, and operational readiness

WHAT WILL YOU BE DOING AS A SENIOR SOFTWARE ENGINEER, GREYSPACE AT SIMSPACE?

• Own technical design and implementation for Greyspace services, defining service boundaries, data ownership, API contracts, and failure behavior in collaboration with technical leads and partner teams.
• Design and build the services that configure, deploy, and manage simulated internet environments. Own critical implementation work and help turn prototypes into maintainable, tested software.
• Develop realistic network and application behavior across DNS, certificates, routing, and services such as web and mail. Validate complete workflows from a range host through the simulated service and back.
• Design for reuse across ranges while isolating configuration, credentials, mutable state, and faults. Work with Security and infrastructure partners to test containment and prevent unintended access between environments or to live networks.
• Develop versioned integration contracts with platform, range, and emulation teams. Partner on operator workflows for configuration, readiness checks, troubleshooting, and lifecycle management.
• Partner with Product and technical leaders to translate training needs into prioritized use cases, explicit acceptance criteria, and incremental delivery plans.
• Own scoping and estimation for assigned projects, making assumptions, dependencies, and trade-offs explicit. Break ambiguous work into useful milestones and validate high-risk decisions with focused technical proofs.
• Drive reliability and operational readiness through automated integration tests, observability, performance testing, recovery procedures, and deployment and upgrade validation for hosted and on-premises environments.
• Participate in design and code reviews, identify and help resolve cross-service technical risks, and improve engineering practices that support reliable delivery.
• Mentor engineers through hands-on collaboration, sharing expertise in distributed systems, networking, testing, and technical decision-making.

WHO YOU ARE:

• 5+ years of software engineering experience with a strong record of building distributed applications, platform services, or networked systems and independently delivering technically complex projects.
• Proven ability to design, build, and ship production-grade distributed services - comfortable owning the full software development lifecycle from architecture through delivery.
• Strong networking fundamentals, including TCP/IP, DNS, HTTP, and TLS, with hands-on experience diagnosing behavior across application, service, and network boundaries.
• Experience designing multi-tenant or distributed systems with clear isolation, state management, API, and failure-recovery boundaries. Familiarity with cyber ranges, simulation, or internet service infrastructure is a plus.
• Demonstrated ability to make sound technical decisions within a team and collaborate effectively with partner teams, balancing idealism with pragmatic delivery.
• Strong scoping and estimation judgment: able to produce an early estimate, identify uncertainty and dependencies, and break complex projects into testable milestones. Helps the team make commitments grounded in evidence and available capacity.
• Strong communicator who can explain complex architecture, networking behavior, and engineering trade-offs to technical and non-technical audiences.
• Proficient in a modern backend programming language and software engineering practices including API design, service decomposition, automated testing, code review, and CI/CD.
• Hands-on experience with Linux, containers, and Kubernetes, including deploying and troubleshooting services. Experience with self-hosted, on-premises, or disconnected environments is a strong plus.
• Comfortable operating with ambiguity - requirements aren't always fully defined, and this role is expected to help clarify them and propose practical solutions. We're looking for someone who drives clarity rather than waiting for it.
• Experience working in security-sensitive or compliance-driven environments (DoD, FedRAMP, SOC 2, or similar) is a strong plus.

We’re proud to offer a competitive and comprehensive package designed to support your well-being, growth, and success:

• Compensation. Base salary range: $160,000 - $225,000, reflecting our confidence in your expertise and impact, with the opportunity for annual bonuses tied to company performance and individual contributions.
• Health & Wellness. Comprehensive medical, dental, and vision benefits, plus savings plans - coverage starts on day one!
• Mental Health Support. Access to company-paid counseling, coaching, and resources for you and your family through Spring Health.
• Financial Well-Being. Plan for your future with a 401(k)-retirement savings plan featuring a company match.
• Flexible Time Off. Take the time you need with unlimited vacation and dedicated health & wellness days. SimSpace provides flexible solutions to meet the diverse work-life needs of team members.
• Parental Leave. Paid leave plans to support you and your loved ones during life’s most important moments.
• Ownership Opportunities: Equity stock options at hire, with annual performance-based grants - become an invested stakeholder in our shared success.
• Referral Rewards: Earn $1,500–$3,500 for every qualified hire through our employee referral program.
• Peloton Interactive Wellness Program: Full- and partial- subsidized membership plans and equipment discounts to help you reach your personalized fitness goals.
• Continuous Learning: Access a LinkedIn Learning membership to prioritize your personal and professional development.
• Social Connections: Monthly reimbursements for meaningful connections with teammates through our SocialSpace Community.
• Extra Perks: Legal plan coverage, pet insurance, wellness reimbursements, and more to simplify life’s details.

SimSpace is an Equal Opportunity Employer:

In compliance with federal law, all persons hired will be required to verify identity and eligibility to work in the United States and to complete the required employment eligibility verification document form upon hire.

SimSpace is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, pregnancy, genetic information, disability, status as a protected veteran, or any other protected category under applicable federal, state, and local laws. We are committed to providing an inclusive and welcoming environment for all members of our staff, clients, volunteers, subcontractors, vendors, and clients.

Research shows that women and people from underrepresented groups only apply to jobs if they meet all of the qualifications. However, no one ever meets 100% of the qualifications. SimSpace encourages you to break that statistic and to apply. We look forward to your application!

We also consider qualified applicants regardless of criminal histories, in accordance with applicable law. We are committed to providing reasonable accommodations for qualified individuals with disabilities in our job application procedures. If you need assistance or accommodation due to a disability, please contact careers@simspace.com.

SimSpace does not accept unsolicited resumes from employment agencies.

Actual compensation for the position is based on a variety of factors, including, but not limited to affordability, skills, qualifications and experience, and may vary from the range.