Senior Software Engineer, Fullstack
About the Role
As a Senior Software Engineer, Fullstack, you'll build core services across our platform, with a strong focus on backend engineering. You'll spend approximately 60% of your time developing and operating backend services in Kotlin/Java and Spring Boot, designing APIs and distributed systems, and building reliable services at scale.
You'll also contribute to the TypeScript/React frontend, spending roughly 40% of your time delivering user-facing features and improvements across the stack.
SimSpace is an AI Proving Ground for cybersecurity, a live-fire cyber range and simulation platform trusted by allied governments, militaries, and Fortune 50 enterprises. Founded in 2015 by experts from U.S. Cyber Command and MIT Lincoln Laboratory, SimSpace enables organizations to train, test, and validate their defenses and AI tools in a safe, realistic environment, with a new platform reaching general availability in August 2026.
Key Responsibilities
Develop and operate backend services primarily in Kotlin/Java and Spring Boot as part of a distributed application for building and simulating cybersecurity ranges.
Design, build, and evolve REST APIs and backend services, with a focus on scalability, reliability, maintainability, and performance.
Build services supporting SimSpace's training and assessment platform for cybersecurity professionals.
Work across the stack, with approximately 60% backend and 40% frontend responsibilities.
Contribute to the TypeScript/React frontend when needed, including state management and user-facing feature development.
Collaborate closely with UX, Product, and Data Science to turn requirements into user-centered, technically sound solutions.
Contribute to technical planning, architecture discussions, and team roadmap decisions.
Deliver high-quality code iteratively with appropriate testing and documentation, balancing scalability and reusability with pragmatic engineering trade-offs.
Support and mentor fellow engineers and participate in regular lunch-and-learns and demos.
Help maintain and improve production services, troubleshooting issues and contributing to the reliability of the platform.
Required Qualifications
Strong bilingual proficiency in English and Spanish across written, virtual, and in-person interactions.
Strong professional experience with Kotlin and/or Java, ideally with Spring Boot.
Strong backend engineering and API design skills.
Experience developing and operating production services at scale.
Solid understanding of software testing principles and practices.
Experience building distributed or service-oriented applications.
Working proficiency with TypeScript and React.js.
Experience with frontend state-management libraries such as Redux, Zustand, or React Query.
Experience working effectively with remote, distributed engineering teams.
Nice to Have
4+ years of industry software-development experience.
Experience with Kubernetes and cloud-native environments.
Experience with Postgres or other relational databases.
Experience with accessibility (a11y) standards.
Familiarity with cybersecurity, networking, or cyber ranges.
Experience with observability, performance optimization, or production troubleshooting.
A bachelor's degree in Computer Science or equivalent experience.
Our Tech Stack
Backend: Kotlin, Java, Spring Boot, Postgres
Frontend: TypeScript, React
Infrastructure: Kubernetes
Location & Work Setup
Remote-first, based in Costa Rica. SimSpace operates remote-first with no designated office; occasional in-region team gatherings, roughly once every few months, may occur, and any required travel is reimbursed.
You'll collaborate with SimSpace's distributed teams across 40+ U.S. states and Costa Rica, so reliable overlap with U.S. time zones and strong English communication are expected.
Engagement begins through an Employer of Record (EOR) and is planned to convert to SimSpace's local Costa Rica entity, anticipated around August–September 2026, at which point you become a full-time SimSpace employee.
Compensation & Benefits
Base salary: Competitive, level-based compensation for a Senior Software Engineer (Level 3), with the exact USD range and payment currency to be confirmed with SimSpace. Annual performance bonuses are tied to company and individual performance, with eligibility for the corporate bonus plan.
Equity: Stock options at hire, with annual performance-based grants.
Health & insurance: Company-paid private medical and life insurance premiums, plus comprehensive medical, dental, and vision benefits.
Statutory: 13th-month payment (aguinaldo) per Costa Rican law.
Mental health: Company-paid counseling and coaching for you and your family through Spring Health.
Parental leave: Paid leave plans.
Referral rewards: $1,500–$3,500 for every qualified referral hire.
Continuous learning: LinkedIn Learning membership.
Connection: Monthly SocialSpace community reimbursements for time with teammates.