Principal Software Engineer - (C# and the .NET Core ecosystem, Python) - Hybrid
Confirmed on the employer's own hiring board on Oct 4, 2026. First seen by Alion on Sep 29, 2026.
FactSet creates flexible, open data and software solutions for over 200,000 investment professionals worldwide, providing instant access to financial data and analytics that investors use to make crucial decisions.
At FactSet, our values are the foundation of everything we do. They express how we act and operate, serve as a compass in our decision-making, and play a big role in how we treat each other, our clients, and our communities. We believe that the best ideas can come from anyone, anywhere, at any time, and that curiosity is the key to anticipating our clients’ needs and exceeding their expectations.
We are seeking an accomplished Principal Software Engineer to join the core team responsible for our mission-critical Investment Book of Record (IBOR). This platform is the definitive source of truth for all positions, transactions, and cash. You will be a key technical contributor, responsible for designing, building, and enhancing the services and interfaces that make our IBOR reliable, scalable, and performant.
Key Responsibilities:
Hands-On Development: Design, develop, and maintain robust backend services and APIs using C# (.NET Core), focusing on high throughput and low latency.
Data & Analytics Tooling: Build data processing pipelines, reconciliation tools, and analytical scripts using Python, leveraging libraries like Pandas and NumPy.
System Architecture: Contribute to architectural and design decisions, ensuring our solutions are scalable, resilient, and maintainable. Participate in code reviews to maintain high standards of quality.
Database Management: Work with our database systems (MongoDB and MySQL) to ensure data integrity and performance.
Collaboration: Work closely with Product Managers to understand requirements.
Mentorship: Guide and mentor junior engineers.
Required Qualifications & Experience:
Minimum Requirements:
10+ years of professional software engineering experience.
Critical Skills:
Expert-level proficiency in C# and the .NET Core ecosystem for building enterprise-grade backend systems.
Strong professional experience with Python for data analysis, scripting, or backend services.
Significant experience in the financial services industry, with a strong grasp of the trade lifecycle, financial instruments (equities, fixed income, derivatives), and position management concepts.
Experience building and consuming RESTful APIs and a solid understanding of software design patterns.
Preferred Qualifications:
Direct experience working on an IBOR or Portfolio Management System
Experience with cloud platforms (AWS) and containerisation technologies (Docker/ ECS).
Experience working with ServiceStack
Education:
Bachelor's degree in Computer Science, Engineering, Mathematics, or a related field.
The budgeted salary range for this position in the states of Connecticut and New York is $165,000.00 - 215,000.00
Company Overview:
FactSet (NYSE:FDS| NASDAQ:FDS) helps the financial community to see more, think bigger, and work better. Our digital platform and enterprise solutions deliver financial data, analytics, and open technology to more than 8,200 global clients, including over 200,000 individual users. Clients across the buy-side and sell-side, as well as wealth managers, private equity firms, and corporations, achieve more every day with our comprehensive and connected content, flexible next-generation workflow solutions, and client-centric specialized support. As a member of the S&P 500, we are committed to sustainable growth and have been recognized among the Best Places to Work in 2023 by Glassdoor as a Glassdoor Employees’ Choice Award winner. Learn more at www.factset.com and follow us on X and LinkedIn.
At FactSet, we celebrate differenceof thought, experience, and perspective.Qualified applicants will be considered for employment without regard to race, color, religion, national origin, sex, sexual orientation, gender identity, disability, protected veteran status or other characteristics protected by law. FactSet participates in E-Verify