Senior .NET Software Engineer

We're looking for a Senior Software Engineer to design, build, and evolve our enterprise data APIs. This role will be actively involved in API architecture and delivery, contribute to a new API catalog and self-service discovery portal, and help drive AI-assisted improvements to how we design, build, and ship APIs. We're looking for someone who combines strong hands-on engineering with the judgment to architect scalable, secure, well-documented APIs — and who's comfortable coordinating across teams to get there. Essential Functions Design, build, and maintain APIs using .NET.Architect API and database solutions for scalability, reliability, and maintainability.Design, optimize and integrate databases - MongoDB, PostgreSQL, MySQL, and OpenSearch - with APIs for efficient data storage, search, and retrieval.Use Kafka for event-driven and streaming integration patterns.Author and maintain API specifications using OpenAPI, ensuring consistent, well-documented API design standards.Contribute to a formal API catalog and registry — a developer portal where teams can discover available API endpoints through natural-language search.Help drive AI-assisted improvements to API development and delivery (e.g., AI-assisted code generation, testing, or monitoring).Debug and troubleshoot production issues using Grafana and related observability tooling.Identify and remediate security vulnerabilities using SonarQube (SAST), DAST tooling, and OWASP Top 10 best practices.Participate in requirement analysis, estimation, and deliverable planning in coordination with cross-functional teams. Qualifications Required Education: Bachelor's degree with 5–7 years of professional software engineering experience, or Master's degree with 3–5 years of experience, with a focus on API development. Required Knowledge And Experience Strong hands-on experience with .NET.Solid experience designing, optimizing, and integrating MongoDB, PostgreSQL, MySQL, and OpenSearch with APIs.Experience with Kafka for messaging/streaming.Experience designing and documenting APIs with OpenAPI.Experience debugging and monitoring production systems using Grafana.Experience identifying and fixing security vulnerabilities using SAST tools (e.g., SonarQube), DAST tools, and OWASP-aligned practices.Strong communication skills, with proven experience in cross-team coordination.Experience with requirement analysis, estimation, and deliverable planning. Preferred Qualifications Experience with Druid or Oracle.Exposure to AI/LLM-assisted development workflows.Experience with API catalog/registry or developer portal tooling. About Fintech For over 35 years, Fintech LLC has redefined how over 1.1 million B2B relationships buy and sell goods and services in the retail, hospitality, and alcohol industries. This integrated platform centralizes invoice data and payments, POS and delivery data, product and cost compliance, price book management, and industry market data using AI, seamless integration capabilities, and proprietary automation technology. Fintech is a Drug-Free Workplace. Fintech is an Equal Opportunity Employer that does not discriminate on the basis of actual or perceived race, color, creed, religion, national origin, ancestry, citizenship status, age, sex or gender (including pregnancy, childbirth and pregnancy-related conditions), gender identity or expression (including transgender status), sexual orientation, marital status, military service and veteran status, physical or mental disability, genetic information, or any other characteristic protected by applicable federal, state, or local laws and ordinances. Fintech’s management team is dedicated to this policy with respect to recruitment, hiring, placement, promotion, transfer, training, compensation, benefits, employee activities, access to facilities and programs and general treatment during employment. We E-Verify.