Sr Software Engineer (React, JavaScript, .net)

Calling all innovators – find your future at Fiserv. We’re Fiserv, a global leader in Fintech and payments, and we move money and information in a way that moves the world. We connect financial institutions, corporations, merchants, and consumers to one another millions of times a day – quickly, reliably, and securely. Any time you swipe your credit card, pay through a mobile app, or withdraw money from the bank, we’re involved. If you want to make an impact on a global scale, come make a difference at Fiserv. Job Title Sr Software Engineer (React, JavaScript, .net) About your role: Join the Client Services technology team as a Full-Stack Web Developer to build and enhance the high-value, data-driven applications that power our global support operations. In this role, you will work across a modern tech stack—utilizing React and TypeScript on the front end alongside C# and ASP.NET Core on the back end—to turn complex business data workflows into secure, scalable, and intuitive user experiences. By partnering with cross-functional business and technical teams, your engineering output will directly improve operational readiness, speed-to-market, and the overall efficiency of our client-facing services ecosystem. What you’ll do: Design, develop, and maintain responsive web applications using React and ASP.NET Core to support modern Single Page Application (SPA) experiences. Build, evolve, and support robust RESTful APIs and backend microservices in C# with a strong emphasis on maintainability, scalability, and clean architecture. Translate complex business needs into well-structured technical solutions, including UI workflows, API contracts, and performant data models. Develop, optimize, and maintain SQL Server database schemas, T-SQL queries, stored procedures, and advanced indexing strategies to support high-volume data use cases. Implement enterprise-grade security practices, including secure coding patterns, robust authentication/authorization protocols, and least-privilege access controls. Create reusable, tested front-end components and backend services using modular design patterns that facilitate long-term codebase health. Collaborate closely with product owners, technical analysts, and cross-functional support teams to reliably deliver features from concept and build to release and support. Participate actively in code reviews, system troubleshooting, performance tuning, and production monitoring to ensure top-tier software quality. Contribute to essential technical documentation, including design notes, operational runbooks, and supportability guides to enhance team velocity. Responsibilities listed are not intended to be all-inclusive and may be modified as necessary. Experience you’ll need to have: Bachelor’s degree in Computer Science, Management Information Systems (MIS), or equivalent practical/professional work experience. 5+ years of professional hands-on experience designing, building, delivering, and supporting full-stack web applications. Strong backend proficiency in C# and modern .NET development (ASP.NET Core). Strong frontend proficiency in React utilizing modern patterns, including functional components, custom hooks, and component design. Production experience using TypeScript and modern JavaScript (ES6+) alongside HTML5 and CSS3 with an awareness of responsive layouts and accessibility. Solid database expertise with SQL Server and T-SQL, including data modeling, advanced querying, and schema optimization. Proven experience building, securing, and consuming REST APIs for client-device and web-client interactions. Familiarity with modern software development practices, including Git-based version control (advanced branching and merging), CI/CD concepts, automated unit/integration testing, and log-based production troubleshooting. Excellent written and verbal communication skills with the ability to work cross-functionally and translate business requirements into software solutions. Experience that would be great to have: Experience utilizing Entity Framework Core or an equivalent Object-Relational Mapping (ORM) framework. Practical experience implementing authentication and authorization standards (e.g., OAuth2, JWT, or Microsoft Entra ID). Familiarity with containerization (Docker) and deploying workloads across cloud ecosystems (Azure/AWS) or hybrid/on-prem environments. Knowledge of asynchronous messaging patterns, queuing architectures, and background processing jobs. Exposure to enterprise reporting, data analysis, or embedded analytics tools such as SSRS or Power BI. Previous engineering experience within the payments, fintech, or financial services industries. Comfort working with modern engineering tooling, including Visual Studio/VS Code, SSMS, Azure DevOps, GitHub Actions, or IIS. How you’ll work: This role is on-site Monday through Friday. Fiserv considers in-person collaboration to be an essential part of this role as in-person office experiences help you with your overall onboarding experience and leads to stronger productivity. This role requires use of a computer and audio equipment. Travel: Approximately 10% travel off-site or to other office locations is expected. Sponsorship: You must currently possess valid and unrestricted U.S. work authorization to be considered for this role. Individuals with temporary visas including, but not limited to, F-1 (OPT, CPT, STEM), H-1B, H-2, or TN, or any candidate requiring sponsorship, now or in the future, will not be considered for this role. Benefits at Fiserv: Fuel Your Life program to support your physical, financial, social, and emotional well-being Paid holidays and generous time away policies No-cost mental health support through Employee Assistance Programs Living Proof program to recognize your peers’ extra effort with points redeemable for rewards Eight Employee Resource Groups to foster a collaborative culture and expand your network ·Unparalleled professional growth with training, development, and internal mobility opportunities Medical, dental, vision, life, and disability insurance options available from day one Retirement planning and discounted shares with the Employee Stock Purchase Plan Tuition assistance and reimbursement program Paid parental, caregiver, and military leave #LI-SH2 Salary Range: $90,000.00-$127,000.00 These pay ranges apply to employees in Maryland. Pay ranges for employees in other states may differ. Certain Positions are Commissions eligible. It is unlawful to discriminate against a prospective employee due to the individual's status as a veteran. Thank you for considering employment with Fiserv. Please: Apply using your legal name Complete the step-by-step profile and attach your resume (either is acceptable, both are preferable). Our commitment to Equal Opportunity: Fiserv is proud to be an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, national origin, gender, gender identity, sexual orientation, age, disability, protected veteran status, or any other category protected by law. If you have a disability and require a reasonable accommodation in completing a job application or otherwise participating in the overall hiring process, please contact View email address on click.appcast.io. Please note our AskHR representatives do not have visibility to your application status. Current associates who require a workplace accommodation should refer to Fiserv’s Disability Accommodation Policy for additional information. Note to agencies: Fiserv does not accept resume submissions from agencies outside of existing agreements. Please do not send resumes to Fiserv associates. Fiserv is not responsible for any fees associated with unsolicited resume submissions. Warning about fake job posts: Please be aware of fraudulent job postings that are not affiliated with Fiserv. Fraudulent job postings may be used by cyber criminals to target your personally identifiable information and/or to steal money or financial information. Any communications from a Fiserv representative will come from a legitimate Fiserv email address. There's a reason why Fiserv is the global leader in information management and electronic commerce systems for the financial services industry. It's our people. If you are a talented professional who gets excited by the challenge of helping Fiserv lead the transformation of financial services technology for our clients' benefit, we encourage you to explore career opportunities with Fiserv, where turning possibilities into realities is the norm.