Senior Software Engineer, Frontend

About the Company America is under sustained cyber attack. Our adversaries infiltrate our networks, steal our IP, and degrade the digital infrastructure that modern life runs on. They’ve learned—correctly—that those attacks rarely produce consequences. Twenty was founded to change that, by making our adversaries think twice before they attack us. Our vision is American and allied primacy in cyberspace—a future where they cannot contest us, deterrence is assured, and the free world remains secure. Founded in 2024, Twenty Technologies ( www.twenty.io ) industrializes offensive cyber operations for the U.S. and its allies. Headquartered in Arlington, Virginia, Twenty has raised $168M from Khosla Ventures, Accel, Caffeinated Capital, Friends & Family Capital, Point72 Ventures, General Catalyst, and In-Q-Tel. Mission | On Site | Full Time | U.S. Citizenship Required / No Active Clearance Required Role Summary You'll be a high-output engineer building mission-critical operator experiences — implementing complex, high-performance interfaces that visualize real-time cyber operation data with speed and precision. You'll contribute meaningfully to frontend architecture and design decisions, own significant features end-to-end, and raise the quality of the codebase around you. You'll work closely with other frontend engineers and cross-functional partners across backend, product, design, and operations to ship capabilities that must work reliably in both cloud and on-premises environments. What You'll Do Build sophisticated React/TypeScript features and components that operate reliably at scale. Implement real-time UI experiences for complex cyber operation data, optimizing for speed and clarity. Contribute to frontend architecture and design decisions alongside your teammates. Build and maintain interactive visualization components (e.g., graphs, timelines, streaming views). Write and maintain automated tests across unit, integration, and end-to-end layers. Participate actively in code review — giving and receiving feedback that raises the quality bar. Identify and address performance issues, technical debt, and reliability gaps proactively. Collaborate with design, product, backend, and operations to deliver well-integrated features. Support engineers through pairing and practical feedback on their work. Who You Are You care about building software that has real-world impact in high-stakes environments. You write clean, precise, and well-tested code and hold yourself to that standard without being asked. You think carefully about performance, reliability, accessibility, and maintainability as you build. You make sound tradeoffs under constraints and communicate them clearly to teammates. You're drawn to complex data problems and enjoy turning them into interfaces that help users act quickly. You take ownership of your work end-to-end — from design review to production — and take pride in delivering on your commitments. You default to secure engineering practices and treat trust, safety, and correctness as non-negotiable. Must Have You have 5–8 years of professional frontend software development experience. You have strong, production-tested expertise in React.js and TypeScript. You have solid command of modern web fundamentals (JavaScript/TypeScript, HTML, CSS). You have experience building and shipping features for performance at scale (profiling, optimization, rendering strategies). You have hands-on experience with automated testing frameworks (e.g., Vitest, React Testing Library, Playwright or Cypress). You have experience with state management patterns and libraries (e.g., Redux, Zustand, or React Query). You have experience with modern build tooling (e.g., Vite or Webpack) and CI/CD pipelines. You collaborate effectively with product and design to deliver high-quality UX. You have strong command of Git in a professional engineering environment, including branch workflows, code review practices, and CI integration. You have a Bachelor's degree in CS/Engineering (or equivalent practical experience). Nice to Have You have experience with complex data visualization (e.g., D3.js, Chart.js, or similar). You have exposure to graph databases or graph query patterns (e.g., Neo4j). You have experience with real-time streaming data and live system visualization. You have worked in defense, security, or other mission-critical domains. You have built UI experiences that surface AI/ML outputs in operational workflows. You have experience contributing to component libraries or design systems (e.g., Storybook). Benefits What's on the table: Health. Medical, dental, and vision plan options. Life / AD&D, disability coverage options. Family. Paid parental leave for eligible full-time employees. 12 weeks for birthing parents, 4 for non-birthing parents, 6 weeks for adoptive, foster, or intended parents through surrogacy. Vacation. Paid holidays and flexible PTO. Take what you need. Retirement. 401(k) with pre-tax and Roth options. HSA/FSA options, dependent care FSA. Benefits vary by location, role, and eligibility. Full plan details provided during the interview and offer process. If this role sounds like you, apply and share with us your interest Due to U.S. government contract and security requirements, this role is limited to U.S. citizens . Some positions may also require eligibility to obtain and maintain a U.S. Government security clearance. Any active clearance requirement will be listed in the role description . Twenty is an equal opportunity employer. We consider all qualified applicants without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, veteran status, disability, or any other protected status, consistent with applicable law. If you need a reasonable accommodation during the hiring process, let us know and we will work with you.