Staff Fullstack Software Engineer, Core Performance

Staff Fullstack Software Engineer, Core Performance This is a high-impact, staff-level engineering role focused on one of the most critical and visible challenges in consumer software: performance across all user-facing surfaces. You will own and define the discipline of performance engineering across web, mobile, and desktop experiences, ensuring millions of users experience fast, reliable product interactions. The role begins with deep hands-on work on high-traffic web applications, then expands into cross-platform leadership across iOS, Android, and desktop systems. You will operate at the intersection of frontend, backend, measurement systems, and product analytics to identify and resolve system-wide bottlenecks. This position requires strong technical leadership to set performance standards, build measurement systems, and drive cross-org alignment. You will also play a key role in shaping AI-assisted engineering workflows to improve productivity and engineering velocity across teams. This is a rare opportunity to define a new engineering function with direct impact on user experience at massive global scale. Accountabilities • Own and drive end-to-end performance improvements across consumer-facing surfaces, starting with web and expanding across mobile and desktop platforms. • Profile and optimize high-traffic web applications, including React-based surfaces, using tools such as flame graphs, heat maps, and RUM data. • Identify and execute high-impact performance improvements, ensuring measurable gains in user experience and system efficiency. • Define and implement performance measurement frameworks, instrumentation, and regression detection systems across engineering teams. • Lead cross-platform performance strategy across iOS, Android, and desktop in collaboration with platform engineering teams. • Write and ship production code in JavaScript/React, with additional backend contributions in Py