Essential Responsibilities: . Take end-to-end ownership of company's existing fiat/payment backend, ensuring stable operation and fast iteration during platform scaling. . Participate in backend service development, ensuring system security and high availability. . Communicate with stakeholders to understand requirements, support business development, and drive service launches. . Continuously optimize system architecture and tackle key technical challenges. . Understand product workflows and leverage technology to drive business growth. Requirements . 5-10 years of backend engineering experience in production systems strong preference for candidates who have owned and evolved an existing platform (not only built new services). . Hands-on experience building or operating fiat payment systems such as on/off-ramps, bank transfers, card payments, ACH/wire/SEPA/FPS/PayNow, or local rails. . Familiar with payment lifecycle: authorization → capture/settlement →refunds/chargebacks → reconcili...