This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Desenvolvedor Back-end .NET Sênior based in Brazil. As a Senior Back-end .NET Developer, you will build and evolve high-availability APIs and services powering digital promotions, sweepstakes, incentive campaigns, and cashback operations. You will work on solutions supporting multiple clients, particularly within the financial services sector. The role combines modern .NET development with legacy system maintenance, domain-driven design, integrations, and secure software engineering. You will contribute to scalable and reliable architectures while working with cloud, messaging, caching, and container technologies. Security and performance are central to the role, including practices aligned with PCI requirements. You will join a fully remote, collaborative environment that values technical learning, transparency, autonomy, and continuous improvement.