Senior Mainframe Developer Jobs in Colorado

Overview

We're hiring an experienced and motivated Senior Software Developer in our National Technology Practice to support key internal and external clients from one of our many hub offices across the U.S.

Your role

• Lead and participate in the design, development, and delivery of enterprise applications using modern technologies including C#, .NET (Razor/Blazor), Python and JavaScript/Node.js
• Collaborate with clients and stakeholders to analyze business needs, define scope, and translate requirements into technical specifications and scalable software solutions.
• Design and develop backend services, APIs, and data-driven Web, desktop and mobile applications, ensuring high performance, reliability, and maintainability.
• Contribute to and lead application architecture and system design leveraging established design patterns and reusable frameworks.
• Develop, maintain, and optimize SQL-based data solutions, including:
• Writing and maintaining SQL scripts
• Designing stored procedures, views, and data transformations
• Supporting data integrity and performance tuning
• Participate in DevOps best practices, including:
• Building and maintaining CI/CD pipelines in Azure DevOps
• Managing code repositories using Git
• Supporting automated build, release, and deployment processes
• Work across development, test, and production environments, ensuring smooth deployments, environment consistency, and release quality.
• Develop high-quality, well-documented code that adheres to best practices and coding standards, minimizing rework and ensuring long-term maintainability.
• Lead or contribute to code reviews, mentoring junior developers and promoting continuous improvement in development standards.
• Produce and maintain technical documentation, including system diagrams, data documentation, and design artifacts, clearly communicating architectural decisions.
• Provide database design and management expertise, ensuring efficient data models and alignment with application requirements.
• Participate in or lead software development best practices initiatives, helping define standards, improve processes, and drive engineering excellence.

About you

• Bachelor's degree (B.S. or B.A.) in Computer Science, Information Technology, or a related discipline; or equivalent experience with four or more years of relevant programming experience in engineering or a related field.
• This level is typically achieved with 8–10+ years of professional experience in software development or related areas.
• Experience applying AI and machine learning technologies (e.g., large language models, computer vision) to enhance enterprise applications, automate workflows, and deliver data-driven solutions.
• Ability to integrate AI capabilities into software development workflows using tools such as GitHub Copilot to improve productivity, accelerate delivery, and maintain code quality.
• Preferred experience with:
• Enterprise software solutions
• Power BI
• SharePoint
• SQL Server and other relational databases (e.g., Postgres, Oracle)
• Experience with C# and the .NET platform, including ASP.NET Core
• Experience with Python preferred
• Experience with JavaScript/TypeScript and Node JS.
• Strong background in database design and/or administration of enterprise relational database management systems.
• Demonstrated excellent interpersonal, communication, and technical writing skills.

Rewards & benefits

At AtkinsRéalis, our values—Safety, Integrity, Collaboration, Innovation, and Excellence—are more than just words. They are the foundation of who we are and how we work. These principles shape our culture, guide our decisions, and inspire us to create an environment where every team member feels empowered to grow, succeed, and make a meaningful impact.

Depending on your employment status, AtkinsRéalis benefits may include medical, dental, vision, company-paid life and short- and long-term disability benefits, employer-matched 401(k) with 100% vesting, employee stock purchase plan, Paid Time Off, leaves of absences options, flexible work options, recognition and employee satisfaction programs, employee assistance program, and voluntary benefits.

About AtkinsRéalis

We're AtkinsRéalis, a world-class engineering services and nuclear organization. We connect people, data and technology to transform the world's infrastructure and energy systems. Together, with our industry partners and clients, and our global team of consultants, designers, engineers and project managers, we can change the world. We're committed to leading our clients across our various end markets to engineer a better future for our planet and its people.

Additional information

Expected compensation range is between $80k-$130k+ annually depending on skills, experience, and geographical location.

Are you ready to expand your career with us? Apply today and help us shape something extraordinary.

AtkinsRéalis is an equal opportunity, Drug-Free employer EOE/Veteran/Disability

Applications for this position are accepted on a rolling basis; no application deadline applies.

AtkinsRéalis cares about your privacy and is committed to protecting your privacy. Please consult our Privacy Notice on our Careers site to know more about how we collect, use and transfer your Personal Data. By submitting your personal information to AtkinsRéalis, you confirm that you have read and accept our Privacy Notice.

Note to staffing and direct hire agencies:

In the event a recruiter or agency who is not on our preferred supplier list submits a resume/candidate to anyone in the company, AtkinsRéalis family of companies, we explicitly reserve the right to recruit and hire the candidate(s) at our discretion and without any financial obligation to the recruiter or agency.