Senior Software Engineer - Frontend UI

Join us in bringing joy to customer experience. Five9 is a leading provider of cloud contact center software, bringing the power of cloud innovation to customers worldwide. Living our values everyday results in our team-first culture and enables us to innovate, grow, and thrive while enjoying the journey together. We celebrate diversity and foster an inclusive environment, empowering our employees to be their authentic selves. Role purpose The Core Applications team is doing greenfield work, introducing new concepts and capabilities to our suite of UI products on a modern React + TypeScript stack. As a Senior Software Engineer, you'll own significant portions of the codebase, drive technical decisions, and mentor fellow engineers. You'll collaborate closely with a distributed team across Australia and the US. This is a high-ownership role on a small, self-organizing team with direct visibility into a major product milestone. How You Contribute • Build and ship features on the new agent desktop in React + TypeScript + Nx, using AI coding agents as part of the daily workflow. • Review and approve pull requests and provide constructive feedback that raises overall application quality. • Mentor fellow engineers and help set the technical bar for the team. • Collaborate async-first with engineering, product, and design across distributed time zones. • Contribute to architectural decisions and async planning via written documentation, Jira, and Confluence. Skills, Competencies And

Required: • Strong React and TypeScript proficiency; experience with other modern frameworks (Vue, Angular, Svelte) is a good signal. • Testing experience with Jest and/or Playwright, with an understanding of the value of thorough test coverage. • Able to operate autonomously on a small, fast-paced team; fills gaps and makes reasonable calls without constant direction. • Strong written communication and collaboration skills for a remote, async-first, distributed environment. • Comfortable conducting code reviews, providing constructive feedback, and mentoring less experienced engineers. • Prior experience using AI coding tools and a genuine willingness to evolve those skills as the space changes. • Bachelor's degree (or equivalent) in a relevant discipline. Desirable: • Prior experience in CCaaS, agent desktop, or UI platform roles. • Familiarity with TanStack Query and Zustand. • Web accessibility knowledge; familiarity with WCAG standards and building accessible UIs. • Monorepo and micro-frontend architecture experience; Nx preferred, but PNPM, Lerna, and other tools are good signals. • Experience with WebSockets or real-time application development. Other