OneMain Financial Jobs

We are the leading provider of professional services to the middle market globally, our purpose is to instill confidence in a world of change, empowering our clients and people to realize their full potential. Our exceptional people are the key to our unrivaled, culture and talent experience and our ability to be compelling to our clients. You'll find an environment that inspires and empowers you to thrive both personally and professionally. There's no one like you and that's why there's nowhere like RSM. Temporary Senior Backend Lead Developer - Capital Markets Technology Transformation About the RoleWe are seeking an experienced Senior Backend Lead Developer for a temporary opportunity supporting a large-scale technology transformation for a leading Capital Markets client. In this role, you will provide hands-on technical leadership, shape modern backend architectures, and guide engineering teams delivering high-performance, scalable, API-driven platforms in a complex enterprise environment. This position is ideal for a senior backend engineer who enjoys combining architecture, hands-on development, and team leadership within fast-paced, regulated programs. What You'll Do * Lead backend engineering efforts across multiple Agile teams within a major transformation initiative. Define and implement secure, scalable, and resilient backend and API architectures. * Translate business and functional requirements into technical designs, integration patterns, and reusable frameworks. * Design and build API-driven services using RESTful and microservices patterns, contract-first development, and Swagger/OpenAPI documentation. Support modernization and legacy platform rewrite initiatives, including migration from older technologies and architectural patterns. * Write high-quality, secure, and performant backend code using .NET, C#, and SQL Server. * Build scalable data access components using Dapper ORM. Implement distributed caching solutions such as Apache Ignite or MemSQL to support high-throughput processing. * Integrate messaging and real-time platforms such as Solace or SignalR for event-driven architectures. * Implement logging, monitoring, and observability using enterprise frameworks such as Serilog, ELK, or Splunk-based solutions. * Drive engineering best practices including code quality, security, exception handling, and layered architecture. * Lead code reviews, technical mentoring, and pairing sessions. Promote test-driven development and automated unit testing using xUnit or NUnit with strong coverage expectations. * Establish reusable backend components and shared frameworks to accelerate delivery. * Define and support SDLC and CI/CD practices, including Git-based branching strategies such as GitFlow or trunk-based development. * Partner with DevOps and SRE teams to support CI/CD pipelines using Jenkins, Helios, and automated quality gates. * Contribute to continuous improvement of development standards, workflows, and documentation. * Collaborate closely with architects, product owners, business analysts, QA, and platform teams. Participate in Agile ceremonies and use tools such as Jira, Confluence, and architecture diagramming tools. * Provide hands-on troubleshooting and technical guidance through development and production support phases. What You Bring * 10+ years of backend engineering experience using .NET and C# in enterprise environments. * Strong experience building scalable RESTful APIs, microservices, and API documentation using Swagger/OpenAPI. * Deep experience with SQL Server, Dapper ORM, JSON/XML, and performance tuning. * Experience with distributed caching platforms such as Apache Ignite or MemSQL. * Hands-on experience with messaging and event-driven architectures using Solace, SignalR, or similar technologies. * Strong background in unit testing, TDD, and automated test pipelines using xUnit or NUnit. * Practical experi