job summary: Sr. Software Development Engineer (Onsite) Locations (Strictly Onsite): * Greenwood Village, CO * Berkeley Heights, NJ * Omaha, NE Compliance & Work Authorization: * Green Card Holders: Must have been living and working in the United States for at least the last 3 years. Background Check: Extensive 6-week process required post-offer. location: Greenwood Village, Colorado job type: Contract to Perm salary: $70 - 80 per hour work hours: 8am to 5pm education: No Degree Required responsibilities: Key Responsibilities Design, build, and maintain applications using Java, Spring/Spring Boot/Spring Security as well as C#, .NET Framework, .NET Core, or .NET 6/7+ Develop RESTful APIs, microservices, and backend services Integrate applications with databases using Entity Framework (EF) / EF Core and SQL Server Collaborate with cross-functional teams using Agile/Scrum methodologies Write clean, maintainable, and scalable code following industry best practices Conduct code reviews, troubleshoot issues, and perform performance optimizations Maintain and enhance CI/CD pipelines using tools such as GitHub Actions, Azure DevOps, etc. Ensure application security using best practices such as authentication, authorization, and OWASP guidelines Create documentation and participate in architectural discussions qualifications: Required Skills & Qualifications 6+ years of back-end development experience Strong proficiency in Java as well as C# and the .NET ecosystem Experience with Spring/Spring Boot/Spring Security Experience with ASP.NET Core, MVC, and Web API Working knowledge of SQL Server, Entity Framework, LINQ Familiarity with Azure (App Services, Functions, Storage, Key Vault) Knowledge of OOP, SOLID principles, and design patterns Experience with unit testing (xUnit, MSTest, NUnit) Strong understanding of REST architecture Proficiency with Git and CI/CD Excellent debugging and problem‑solving skills Preferred Qualifications Experience with microservices architecture Knowledge of Docker and containerized deployments Exposure to Blazor, React, or Angular Experience with message brokers like Azure Service Bus, RabbitMQ, or Kafka Equal Opportunity Employer: Race, Color, Religion, Sex, Sexual Orientation, Gender Identity, National Origin, Age, Genetic Information, Disability, Protected Veteran Status, or any other legally protected group status.At Randstad Digital, we welcome people of all abilities and want to ensure that our hiring and interview process meets the needs of all applicants. If you require a reasonable accommodation to make your application or interview experience a great one, please contact HRsupport@randstadusa.com. Pay offered to a successful candidate will be based on several factors including the candidate's education, work experience, work location, specific job duties, certifications, etc. In addition, Randstad Digital offers a comprehensive benefits package, including: medical, prescription, dental, vision, AD&D, and life insurance offerings, short-term disability, and a 401K plan (all benefits are based on eligibility). This posting is open for thirty (30) days.