| C# Backend Developer | Senior

Description

**[C# Backend Developer | Senior]** Remote | 44 hours per week **To learn more about us** We develop people, software & businesses +16 years of experience developing software across 4 continents with an NPS of +84, placing us in the excellence zone! We specialize in digital solutions (web, mobile, BI, RPA, etc.), with offices in São Paulo, Porto Alegre, Belo Horizonte, and the USA. **Opportunity Overview:** * We are seeking a Mid-to-Senior Backend Developer to enhance our financial hub, primarily focusing on implementing and maintaining banking and payment integrations. The professional will directly develop integrations related to bank collections, hybrid boleto (Bolecode), PIX, card acquirers, and consumption of secure REST APIs within a mission-critical, corporate legacy environment. **Responsibilities and Duties:** * Interpret technical banking documentation; * Understand REST contracts and complex payloads; * Work in a legacy environment without requiring immediate modernization; * Investigate end-to-end issues; * Develop resilient and sustainable integrations; * Design retry and fallback mechanisms; * Ensure traceability of financial transactions; * Support technical and architectural decisions; * Work with technical autonomy and a strong sense of ownership. **Required Skills:** * Solid backend development experience in C#; * Experience with .NET Framework 4.x; * Experience with ASP.NET MVC/Web API; * Knowledge of consuming authenticated REST APIs via OAuth2; * Experience with financial integrations, banking APIs, and payment methods; * Knowledge of secure HTTP/HTTPS integrations; * Experience with digital certificates (.crt, .key, .pem, and .pfx); * Knowledge of mTLS (Mutual TLS), TLS, and SSL configuration; * Experience with JSON serialization/deserialization; * Experience handling timeouts, retries, and communication failures; * Knowledge of idempotency and transaction reprocessing; * Experience with SQL Server (queries, stored procedures, troubleshooting); * Version control with Git; * Ability to troubleshoot HTTP, TLS, SSL, certificate, and OAuth errors; **Preferred Skills:** * Prior experience with banking APIs, especially Itaú and Santander; * Knowledge of Bolecode, registered collections, and PIX integrations; * Experience with card acquirers such as Cielo, Getnet, and Rede; * Experience with transaction capture, cancellation, and reconciliation; * Experience with ERP systems and financial environments; * Knowledge of banking certification processes; * Experience with observability and monitoring; * Strong communication skills, technical autonomy, and sense of ownership; * Ability to operate in highly critical corporate environments; * Experience with agile methodologies. **What You’ll Find at GX2:** * Original content hub segmented by learning tracks (AI, QA, Agility, UX/UI Design, Product, Software Development); * Monthly talks focused on soft skills development; * Culture of care for people and mental health; * Mental health and well-being platform; * GX2 Follow Up: Individual monthly check-ins focused on well-being and professional development. **A Message from GX2:** This position is open to all interested individuals. We work daily to build a diverse and plural environment that values and respects differences, and we champion the freedom to be who you are — free from stereotypes and prejudice.