Hopper is seeking a Senior Full Stack Engineer (Realtime & Voice) to anchor the real-time and voice layer end-to-end. You will build across React/TypeScript front ends, Scala and Python services, and cloud infrastructure to serve multiple partners from one codebase. This is a high-ownership role in a fast-growing fintech travel platform based in Barcelona. Design for multi-tenant scale, implement safety guardrails, and drive reliable, low-latency experiences from code to customer touchpoints.